CoolWiki - User contributions [en]

Summaries and questions on discussed papers

2012-05-17T17:31:08Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

[[File:UH 2.2 telescope.jpg]]
[[File:UH 2.2 telescope 2.jpg]]

University of Hawaii 2.2-m (87 inch) telescope on Mauna Kea using the Wide Field Grism Spectrograph 2.

''Highlights of the Paper:''

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.

* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.
* Did not find any H alpha PMS stars in SFO 38 (BRC 38), but Choudhury (2010) found 45 YSOs in and around
SFO 38. "Of these, 26 sources are Class-0/I, Class-I, and Class-I/II, but there are no such objects situated outside the ionized
rim. It follows that the birth of low-mass stars associated with bright rims appears to be the primary mode of star formation in IC 1396 at present."
* Young low-mass stars, which probably formed by a triggered mechanism in the BRC region, contribute a fraction of the mass of stars in IC 1396.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Compared emission stars with the Two Micron All Sky Survey (2MASS).
* Compared results to MIR All-Sky Survey obtained with the infrared camera (IRC) on board the AKARI satellite.

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.
* Radiation-driven implosion may have triggered star formation--after the formation of HD 206267.
* HD 206267 was likely born in the central part after the continuous low mass star formation.

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand and then the star accelerates the star forming process?

* Figure 1, page 31, shows where BRC 34 & 38 are located in their study. Paper states that BRC 38 is much more active forming stars but does not say exactly how many of the 639?? It says "Note. — Table 2 is published in its entirety in the electronic edition of Astronomical Journal. A portion is shown here..."

FROM OUR PREVIOUS SUMMARY: We need to: "read this in some detail, and scavenge the data in the regions we care about (BRC 34 and 38)."

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

'''REMINDER DEFINITION:''' (from wiki) In astronomy, color–color diagrams are a means of comparing the apparent magnitudes of stars at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color. On color–color diagrams, the color defined by two wavelength bands is plotted on the horizontal axis, and then the color defined by another brightness difference (though usually there is one band involved in determining both colors) will be plotted on the vertical axis.

NOTE: It would help if figures were placed within the text.

'''COMPARISON to BARENSTEN:''' Out of 143 PMS candidates identified by Barentsen, 119 stars are in common with our HII sample.
For the PMS candidates including smaller EW ( > 10 °A ), the fraction of recovered sources by Barentsen et al. (2011) falls off to 50%.

On the other hand, the fraction of recovered sources with EW > 10 °A maintains 86% (51 out of 59) in our sample. We confirmed that none of their rejected candidates ( 30 stars ) by Barentsen were included in our list. Thus, our observations are more sensitive than their survey for the emission-line stars with small H alpha equivalent width.

ACRONYMS: Great list: http://en.wikipedia.org/wiki/List_of_astronomy_acronyms
http://www.all-acronyms.com
EW = Equivalent Widths
CTTS = Classical T tauri Stars
WTTS = Weak-line T tauri Stars

'''QUESTION:''' What is the AeBe in HAeBe stars? Herbig Ae/Be (HAEBE) stars are pre main-sequence stars of intermediate mass (2
to 9 solar masses). With masses between those of low-mass T Tauri stars and high mass young stars, HAEBE stars ﬁll an important parameter space in addressing the question of star formation as a function of mass.

Found this Powerpoint when researching:
http://www.google.com/url?sa=t&rct=j&q=ysos%20tts%20pms&source=web&cd=3&ved=0CFUQFjAC&url=http%3A%2F%2Fhomepages.spa.umn.edu%2F~pedmon%2FT%2520Tauri%2520Stars%252012-05-05.ppt&ei=fC21T9aPFsWigweTmIjeDw&usg=AFQjCNHna3ure4nC6BQe5irp9V8wT0yyJw

[[File:YSO Evolution.jpg]]
Diagram on YSO evolution from powerpoint

''Young Stellar Objects are:''
* Objects contracting out of a molecular cloud
* Pre-Main Sequence (PMS)
* Go from Contraction to Convection to Radiation
* Time scales to reach the Zero Age Main Sequence (ZAMS) vary depending on Mass of Star

''T Tauri Stars are:''
* A subclass of YSO’s
* CTTS mark the change from Gravitational Collapse to Internal Convection of the Protostar
* WTTS mark the change from Convection Transport to Radiation Transport
* WTTS also mark when Hydrogen Fusion become dominate in a Protostar
* Need better understanding of the disk and jets are needed to fully understand T Tauri Stars
* T Tauri Stars give insight to how our Sun evolved on to the Main Sequence

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T17:29:34Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

[[File:UH 2.2 telescope.jpg]]
[[File:UH 2.2 telescope 2.jpg]]
University of Hawaii 2.2-m (87 inch) telescope on Mauna Kea using the Wide Field Grism Spectrograph 2.

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.
* Did not find any H alpha PMS stars in SFO 38 (BRC 38), but Choudhury (2010) found 45 YSOs in and around
SFO 38. "Of these, 26 sources are Class-0/I, Class-I, and Class-I/II, but there are no such objects situated outside the ionized
rim. It follows that the birth of low-mass stars associated with bright rims appears to be the primary mode of star formation in IC 1396 at present."
* Young low-mass stars, which probably formed by a triggered mechanism in the BRC region, contribute a fraction of the mass of stars in IC 1396.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Compared emission stars with the Two Micron All Sky Survey (2MASS).
* Compared results to MIR All-Sky Survey obtained with the infrared camera (IRC) on board the AKARI satellite.

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation--after the formation of HD 206267.
* HD 206267 was likely born in the central part after the continuous low mass star formation.

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand and then the star accelerates the star forming process?

* Figure 1, page 31, shows where BRC 34 & 38 are located in their study. Paper states that BRC 38 is much more active forming stars but does not say exactly how many of the 639?? It says "Note. — Table 2 is published in its entirety in the electronic edition of Astronomical Journal. A portion is shown here..."

FROM OUR PREVIOUS SUMMARY: We need to: "read this in some detail, and scavenge the data in the regions we care about (BRC 34 and 38)."

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

'''REMINDER DEFINITION:''' (from wiki) In astronomy, color–color diagrams are a means of comparing the apparent magnitudes of stars at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color. On color–color diagrams, the color defined by two wavelength bands is plotted on the horizontal axis, and then the color defined by another brightness difference (though usually there is one band involved in determining both colors) will be plotted on the vertical axis.

NOTE: It would help if figures were placed within the text.

'''COMPARISON to BARENSTEN:''' Out of 143 PMS candidates identified by Barentsen, 119 stars are in common with our HII sample.
For the PMS candidates including smaller EW ( > 10 °A ), the fraction of recovered sources by Barentsen et al. (2011) falls off to 50%.

On the other hand, the fraction of recovered sources with EW > 10 °A maintains 86% (51 out of 59) in our sample. We confirmed that none of their rejected candidates ( 30 stars ) by Barentsen were included in our list. Thus, our observations are more sensitive than their survey for the emission-line stars with small H alpha equivalent width.

ACRONYMS: Great list: http://en.wikipedia.org/wiki/List_of_astronomy_acronyms
http://www.all-acronyms.com
EW = Equivalent Widths
CTTS = Classical T tauri Stars
WTTS = Weak-line T tauri Stars

'''QUESTION:''' What is the AeBe in HAeBe stars? Herbig Ae/Be (HAEBE) stars are pre main-sequence stars of intermediate mass (2
to 9 solar masses). With masses between those of low-mass T Tauri stars and high mass young stars, HAEBE stars ﬁll an important parameter space in addressing the question of star formation as a function of mass.

Found this Powerpoint when researching:
http://www.google.com/url?sa=t&rct=j&q=ysos%20tts%20pms&source=web&cd=3&ved=0CFUQFjAC&url=http%3A%2F%2Fhomepages.spa.umn.edu%2F~pedmon%2FT%2520Tauri%2520Stars%252012-05-05.ppt&ei=fC21T9aPFsWigweTmIjeDw&usg=AFQjCNHna3ure4nC6BQe5irp9V8wT0yyJw

[[File:YSO Evolution.jpg]]
Diagram on YSO evolution from powerpoint

''Young Stellar Objects are:''
* Objects contracting out of a molecular cloud
* Pre-Main Sequence (PMS)
* Go from Contraction to Convection to Radiation
* Time scales to reach the Zero Age Main Sequence (ZAMS) vary depending on Mass of Star

''T Tauri Stars are:''
* A subclass of YSO’s
* CTTS mark the change from Gravitational Collapse to Internal Convection of the Protostar
* WTTS mark the change from Convection Transport to Radiation Transport
* WTTS also mark when Hydrogen Fusion become dominate in a Protostar
* Need better understanding of the disk and jets are needed to fully understand T Tauri Stars
* T Tauri Stars give insight to how our Sun evolved on to the Main Sequence

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T17:26:16Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

[[File:UH 2.2 telescope.jpg]]
[[File:UH 2.2 telescope 2.jpg]]
University of Hawaii 2.2-m (87 inch) telescope on Mauna Kea using the Wide Field Grism Spectrograph 2.

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.
* Did not find any H alpha PMS stars in SFO 38 (BRC 38), but Choudhury (2010) found 45 YSOs in and around
SFO 38. "Of these, 26 sources are Class-0/I, Class-I, and Class-I/II, but there are no such objects situated outside the ionized
rim. It follows that the birth of low-mass stars associated with bright rims appears to be the primary mode of star formation in IC 1396 at present."
* Young low-mass stars, which probably formed by a triggered mechanism in the BRC region, contribute a fraction of the mass of stars in IC 1396.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Compared emission stars with the Two Micron All Sky Survey (2MASS).
* Compared results to MIR All-Sky Survey obtained with the infrared camera (IRC) on board the AKARI satellite.

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation--after the formation of HD 206267.
* HD 206267 was likely born in the central part after the continuous low mass star formation.

* Figure 1, page 31, shows where BRC 34 & 38 are located in their study. Paper states that BRC 38 is much more active forming stars but does not say exactly how many of the 639??

FROM OUR PREVIOUS SUMMARY: We need to: "read this in some detail, and scavenge the data in the regions we care about (brc 34 and 38)."

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand?

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

'''REMINDER DEFINITION:''' (from wiki) In astronomy, color–color diagrams are a means of comparing the apparent magnitudes of stars at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color. On color–color diagrams, the color defined by two wavelength bands is plotted on the horizontal axis, and then the color defined by another brightness difference (though usually there is one band involved in determining both colors) will be plotted on the vertical axis.

NOTE: It would help if figures were placed within the text.

'''COMPARISON to BARENSTEN:''' Out of 143 PMS candidates identified by Barentsen, 119 stars are in common with our HII sample.
For the PMS candidates including smaller EW ( > 10 °A ), the fraction of recovered sources by Barentsen et al. (2011) falls off to 50%.

On the other hand, the fraction of recovered sources with EW > 10 °A maintains 86% (51 out of 59) in our sample. We confirmed that none of their rejected candidates ( 30 stars ) by Barentsen were included in our list. Thus, our observations are more sensitive than their survey for the emission-line stars with small H alpha equivalent width.

ACRONYMS: Great list: http://en.wikipedia.org/wiki/List_of_astronomy_acronyms
http://www.all-acronyms.com
EW = Equivalent Widths
CTTS = Classical T tauri Stars
WTTS = Weak-line T tauri Stars

'''QUESTION:''' What is the AeBe in HAeBe stars? Herbig Ae/Be (HAEBE) stars are pre main-sequence stars of intermediate mass (2
to 9 solar masses). With masses between those of low-mass T Tauri stars and high mass young stars, HAEBE stars ﬁll an important parameter space in addressing the question of star formation as a function of mass.

Found this Powerpoint when researching:
http://www.google.com/url?sa=t&rct=j&q=ysos%20tts%20pms&source=web&cd=3&ved=0CFUQFjAC&url=http%3A%2F%2Fhomepages.spa.umn.edu%2F~pedmon%2FT%2520Tauri%2520Stars%252012-05-05.ppt&ei=fC21T9aPFsWigweTmIjeDw&usg=AFQjCNHna3ure4nC6BQe5irp9V8wT0yyJw

[[File:YSO Evolution.jpg]]
Diagram on YSO evolution from powerpoint

''Young Stellar Objects are:''
* Objects contracting out of a molecular cloud
* Pre-Main Sequence (PMS)
* Go from Contraction to Convection to Radiation
* Time scales to reach the Zero Age Main Sequence (ZAMS) vary depending on Mass of Star

''T Tauri Stars are:''
* A subclass of YSO’s
* CTTS mark the change from Gravitational Collapse to Internal Convection of the Protostar
* WTTS mark the change from Convection Transport to Radiation Transport
* WTTS also mark when Hydrogen Fusion become dominate in a Protostar
* Need better understanding of the disk and jets are needed to fully understand T Tauri Stars
* T Tauri Stars give insight to how our Sun evolved on to the Main Sequence

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T17:12:37Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

[[File:UH 2.2 telescope.jpg]]
[[File:UH 2.2 telescope 2.jpg]]
University of Hawaii 2.2-m (87 inch) telescope on Mauna Kea using the Wide Field Grism Spectrograph 2.

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Compared emission stars with the Two Micron All Sky Survey (2MASS).
* Compared results to MIR All-Sky Survey obtained with the infrared camera (IRC) on board the AKARI satellite.

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation.

FROM OUR PREVIOUS SUMMARY: We need to: "read this in some detail, and scavenge the data in the regions we care about (brc 34 and 38)."

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand?

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

'''REMINDER DEFINITION:''' (from wiki) In astronomy, color–color diagrams are a means of comparing the apparent magnitudes of stars at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color. On color–color diagrams, the color defined by two wavelength bands is plotted on the horizontal axis, and then the color defined by another brightness difference (though usually there is one band involved in determining both colors) will be plotted on the vertical axis.

NOTE: It would help if figures were placed within the text.

'''COMPARISON to BARENSTEN:''' Out of 143 PMS candidates identified by Barentsen, 119 stars are in common with our HII sample.
For the PMS candidates including smaller EW ( > 10 °A ), the fraction of recovered sources by Barentsen et al. (2011) falls off to 50%.

On the other hand, the fraction of recovered sources with EW > 10 °A maintains 86% (51 out of 59) in our sample. We confirmed that none of their rejected candidates ( 30 stars ) by Barentsen were included in our list. Thus, our observations are more sensitive than their survey for the emission-line stars with small H alpha equivalent width.

ACRONYMS: Great list: http://en.wikipedia.org/wiki/List_of_astronomy_acronyms
http://www.all-acronyms.com
EW = Equivalent Widths
CTTS = Classical T tauri Stars
WTTS = Weak-line T tauri Stars

'''QUESTION:''' What is the AeBe in HAeBe stars? Herbig Ae/Be (HAEBE) stars are pre main-sequence stars of intermediate mass (2
to 9 solar masses). With masses between those of low-mass T Tauri stars and high mass young stars, HAEBE stars ﬁll an important parameter space in addressing the question of star formation as a function of mass.

Found this Powerpoint when researching:
http://www.google.com/url?sa=t&rct=j&q=ysos%20tts%20pms&source=web&cd=3&ved=0CFUQFjAC&url=http%3A%2F%2Fhomepages.spa.umn.edu%2F~pedmon%2FT%2520Tauri%2520Stars%252012-05-05.ppt&ei=fC21T9aPFsWigweTmIjeDw&usg=AFQjCNHna3ure4nC6BQe5irp9V8wT0yyJw

[[File:YSO Evolution.jpg]]
Diagram on YSO evolution from powerpoint

''Young Stellar Objects are:''
* Objects contracting out of a molecular cloud
* Pre-Main Sequence (PMS)
* Go from Contraction to Convection to Radiation
* Time scales to reach the Zero Age Main Sequence (ZAMS) vary depending on Mass of Star

''T Tauri Stars are:''
* A subclass of YSO’s
* CTTS mark the change from Gravitational Collapse to Internal Convection of the Protostar
* WTTS mark the change from Convection Transport to Radiation Transport
* WTTS also mark when Hydrogen Fusion become dominate in a Protostar
* Need better understanding of the disk and jets are needed to fully understand T Tauri Stars
* T Tauri Stars give insight to how our Sun evolved on to the Main Sequence

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T17:08:39Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

[[File:UH 2.2 telescope.jpg]]
[[File:UH 2.2 telescope 2.jpg]]
University of Hawaii 2.2-m (87 inch) telescope on Mauna Kea using the Wide Field Grism Spectrograph 2.

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Compared emission stars with the Two Micron All Sky Survey (2MASS).
* Compared results to MIR All-Sky Survey obtained with the infrared camera (IRC) on board the AKARI satellite.

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation.

FROM OUR PREVIOUS SUMMARY: We need to: "read this in some detail, and scavenge the data in the regions we care about (brc 34 and 38)."

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand?

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

'''REMINDER DEFINITION:''' (from wiki) In astronomy, color–color diagrams are a means of comparing the apparent magnitudes of stars at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color. On color–color diagrams, the color defined by two wavelength bands is plotted on the horizontal axis, and then the color defined by another brightness difference (though usually there is one band involved in determining both colors) will be plotted on the vertical axis.

NOTE: It would help if figures were placed within the text.

'''COMPARISON to BARENSTEN:''' Out of 143 PMS candidates identified by Barentsen, 119 stars are in common with our HII sample.
For the PMS candidates including smaller EW ( > 10 °A ), the fraction of recovered sources by Barentsen et al. (2011) falls off to 50%.

On the other hand, the fraction of recovered sources with EW > 10 °A maintains 86% (51 out of 59) in our sample. We confirmed that none of their rejected candidates ( 30 stars ) by Barentsen were included in our list. Thus, our observations are more sensitive than their survey for the emission-line stars with small H alpha equivalent width.

ACRONYMS: Great list: http://en.wikipedia.org/wiki/List_of_astronomy_acronyms
http://www.all-acronyms.com
EW = Equivalent Widths
CTTS = Classical T tauri Stars
WTTS = Weak-line T tauri Stars

'''QUESTION:''' What is the AeBe in HAeBe stars? Herbig Ae/Be (HAEBE) stars are pre main-sequence stars of intermediate mass (2
to 9 solar masses). With masses between those of low-mass T Tauri stars and high mass young stars, HAEBE stars ﬁll an important parameter space in addressing the question of star formation as a function of mass.

Found this Powerpoint when researching:
http://www.google.com/url?sa=t&rct=j&q=ysos%20tts%20pms&source=web&cd=3&ved=0CFUQFjAC&url=http%3A%2F%2Fhomepages.spa.umn.edu%2F~pedmon%2FT%2520Tauri%2520Stars%252012-05-05.ppt&ei=fC21T9aPFsWigweTmIjeDw&usg=AFQjCNHna3ure4nC6BQe5irp9V8wT0yyJw

[[File:YSO Evolution.jpg]]

Diagram on YSO evolution

Young Stellare Objects:
* Objects contracting out of a molecular cloud
* Pre-Main Sequence (PMS)
* Go from Contraction to Convection to Radiation
* Time scales to reach the Zero Age Main Sequence (ZAMS) vary depending on Mass of Star

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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File:YSO Evolution.jpg

2012-05-17T17:08:21Z

Bonadurer:

Summaries and questions on discussed papers

2012-05-17T17:00:27Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

[[File:UH 2.2 telescope.jpg]]
[[File:UH 2.2 telescope 2.jpg]]
University of Hawaii 2.2-m (87 inch) telescope on Mauna Kea using the Wide Field Grism Spectrograph 2.

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Compared emission stars with the Two Micron All Sky Survey (2MASS).
* Compared results to MIR All-Sky Survey obtained with the infrared camera (IRC) on board the AKARI satellite.

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation.

FROM OUR PREVIOUS SUMMARY: We need to: "read this in some detail, and scavenge the data in the regions we care about (brc 34 and 38)."

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand?

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

'''REMINDER DEFINITION:''' (from wiki) In astronomy, color–color diagrams are a means of comparing the apparent magnitudes of stars at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color. On color–color diagrams, the color defined by two wavelength bands is plotted on the horizontal axis, and then the color defined by another brightness difference (though usually there is one band involved in determining both colors) will be plotted on the vertical axis.

NOTE: It would help if figures were placed within the text.

'''COMPARISON to BARENSTEN:''' Out of 143 PMS candidates identified by Barentsen, 119 stars are in common with our HII sample.
For the PMS candidates including smaller EW ( > 10 °A ), the fraction of recovered sources by Barentsen et al. (2011) falls off to 50%.

On the other hand, the fraction of recovered sources with EW > 10 °A maintains 86% (51 out of 59) in our sample. We confirmed that none of their rejected candidates ( 30 stars ) by Barentsen were included in our list. Thus, our observations are more sensitive than their survey for the emission-line stars with small H alpha equivalent width.

ACRONYMS: Great list: http://en.wikipedia.org/wiki/List_of_astronomy_acronyms
http://www.all-acronyms.com
EW = Equivalent Widths
CTTS = Classical T tauri Stars
WTTS = Weak-line T tauri Stars

'''QUESTION:''' What is the AeBe in HAeBe stars? Herbig Ae/Be (HAEBE) stars are pre main-sequence stars of intermediate mass (2
to 9 solar masses). With masses between those of low-mass T Tauri stars and high mass young stars, HAEBE stars ﬁll an important parameter space in addressing the question of star formation as a function of mass.

Found this Powerpoint:
http://www.google.com/url?sa=t&rct=j&q=ysos%20tts%20pms&source=web&cd=3&ved=0CFUQFjAC&url=http%3A%2F%2Fhomepages.spa.umn.edu%2F~pedmon%2FT%2520Tauri%2520Stars%252012-05-05.ppt&ei=fC21T9aPFsWigweTmIjeDw&usg=AFQjCNHna3ure4nC6BQe5irp9V8wT0yyJw

Young Stellare Objects:
* Objects contracting out of a molecular cloud
* Pre-Main Sequence (PMS)
* Go from Contraction to Convection to Radiation
* Time scales to reach the Zero Age Main Sequence (ZAMS) vary depending on Mass of Star

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T16:54:27Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

[[File:UH 2.2 telescope.jpg]]
[[File:UH 2.2 telescope 2.jpg]]
University of Hawaii 2.2-m (87 inch) telescope on Mauna Kea using the Wide Field Grism Spectrograph 2.

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed
clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Compared emission stars with the Two Micron All Sky Survey (2MASS).
* Compared results to MIR All-Sky Survey obtained with the infrared camera (IRC) on board the AKARI satellite.

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation.

FROM OUR PREVIOUS SUMMARY: We need to: "read this in some detail, and scavenge the data in the regions we care about (brc 34 and 38)."

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand?

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

'''REMINDER DEFINITION:''' (from wiki) In astronomy, color–color diagrams are a means of comparing the apparent magnitudes of stars at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color. On color–color diagrams, the color defined by two wavelength bands is plotted on the horizontal axis, and then the color defined by another brightness difference (though usually there is one band involved in determining both colors) will be plotted on the vertical axis.

NOTE: It would help if figures were placed within the text.

'''COMPARISON to BARENSTEN:''' Out of 143 PMS candidates identified by Barentsen, 119 stars are in common with our HII sample.
For the PMS candidates including smaller EW ( > 10 °A ), the fraction of recovered sources by Barentsen et al. (2011) falls off to 50%.

On the other hand, the fraction of recovered sources with EW > 10 °A maintains 86% (51 out of 59) in our sample. We confirmed that none of their rejected candidates ( 30 stars ) by Barentsen were included in our list. Thus, our observations are more sensitive than their survey for the emission-line stars with small H alpha equivalent width.

ACRONYMS: Great list: http://en.wikipedia.org/wiki/List_of_astronomy_acronyms
http://www.all-acronyms.com
EW = Equivalent Widths
CTTS = Classical T tauri Stars
WTTS = Weak-line T tauri Stars

'''QUESTION:''' What is the AeBe in HAeBe stars? Herbig Ae/Be (HAEBE) stars are pre main-sequence stars of intermediate mass (2
to 9 solar masses). With masses between those of low-mass T Tauri stars and high mass young stars, HAEBE stars ﬁll an important parameter space in addressing the question of star formation as a function of mass.

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T16:45:40Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

[[File:UH 2.2 telescope.jpg]]
[[File:UH 2.2 telescope 2.jpg]]
University of Hawaii 2.2-m (87 inch) telescope on Mauna Kea using the Wide Field Grism Spectrograph 2.

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed
clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Compared emission stars with the Two Micron All Sky Survey (2MASS).
* Compared results to MIR All-Sky Survey obtained with the infrared camera (IRC) on board the AKARI satellite.

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation.

FROM OUR PREVIOUS SUMMARY: We need to: "read this in some detail, and scavenge the data in the regions we care about (brc 34 and 38)."

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand?

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

'''REMINDER DEFINITION:''' (from wiki) In astronomy, color–color diagrams are a means of comparing the apparent magnitudes of stars at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color. On color–color diagrams, the color defined by two wavelength bands is plotted on the horizontal axis, and then the color defined by another brightness difference (though usually there is one band involved in determining both colors) will be plotted on the vertical axis.

NOTE: It would help if figures were placed within the text.

'''COMPARISON to BARENSTEN:''' Out of 143 PMS candidates identified by Barentsen, 119 stars are in common with our HII sample.
For the PMS candidates including smaller EW ( > 10 °A ), the fraction of recovered sources by Barentsen et al. (2011) falls off to 50%.

On the other hand, the fraction of recovered sources with EW > 10 °A maintains 86% (51 out of 59) in our sample. We confirmed that none of their rejected candidates ( 30 stars ) by Barentsen were included in our list. Thus, our observations are more sensitive than their survey for the emission-line stars with small H alpha equivalent width.

ACRONYMS: Great list: http://en.wikipedia.org/wiki/List_of_astronomy_acronyms
http://www.all-acronyms.com
EW = Equivalent Widths

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T16:26:11Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

[[File:UH 2.2 telescope.jpg]]
[[File:UH 2.2 telescope 2.jpg]]
University of Hawaii 2.2-m (87 inch) telescope on Mauna Kea using the Wide Field Grism Spectrograph 2.

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed
clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Compared emission stars with the Two Micron All Sky Survey (2MASS).

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation.

FROM OUR PREVIOUS SUMMARY: We need to: "read this in some detail, and scavenge the data in the regions we care about (brc 34 and 38)."

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand?

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

'''REMINDER DEFINITION:''' (from wiki) In astronomy, color–color diagrams are a means of comparing the apparent magnitudes of stars at different wavelengths. Astronomers typically observe at narrow bands around certain wavelengths, and objects observed will have different brightnesses in each band. The difference in brightness between two bands is referred to as color. On color–color diagrams, the color defined by two wavelength bands is plotted on the horizontal axis, and then the color defined by another brightness difference (though usually there is one band involved in determining both colors) will be plotted on the vertical axis.

NOTE: It would help if figures were placed within the text.

COMPARISON to BARENSTEN: Out of 143 PMS candidates identified by Barentsen, 119 stars are in common with our HII sample.
For the PMS candidates including smaller EW ( > 10 °A ), the fraction of recovered sources by Barentsen et al. (2011) falls off to 50%.

ACRONYMS: Great list: http://en.wikipedia.org/wiki/List_of_astronomy_acronyms
EW = Equivalent Widths

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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File:UH 2.2 telescope 2.jpg

2012-05-17T15:26:36Z

Bonadurer:

File:UH 2.2 telescope.jpg

2012-05-17T15:26:14Z

Bonadurer:

Summaries and questions on discussed papers

2012-05-17T15:25:42Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

[[File:UH 2.2 telescope.jpg]]
[[File:UH 2.2 telescope 2.jpg]]
* University of Hawaii (UH) 2.2-m telescope on Mauna Kea.

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed
clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation.

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand?

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T15:23:50Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

* Used the University of Hawaii (UH) 2.2-m telescope on Mauna Kea.

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri stars-TTS?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed
clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Results may suggest that massive stars were born '''after''' the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation.

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand?

'''DEFINITION:''' Coeval: Two stars thought to be coeval because they have nearly the same mass and brightness.
'''DEFINITION:''' Viriral: The virial theorem provides a general equation relating the average over time of the total kinetic energy.

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T14:58:00Z

Bonadurer: /* Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

* Survey of emission-line stars in the IC 1396 H II (H2) region
* Calls YSOs (or T Tauri?) pre-main sequence (PMS)stars.
* Found 639 H-alpha emission-line stars
* Area was 4.2deg2 and their i′-photometry was measured.
* Spatial distribution shows aggregates near the elephant trunk globule (Rim A) and bright-rimmed
clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267.

* Chose PMS stars based on extinstion estimate from the near-infrared (NIR) color–color diagram.
* Age and mass of these stars were derived from the extinction corrected color-magnitude diagram and
theoretical pre-main sequence tracks. (Most have ages less than 3 million years and masses of 0.2–0.6 mass of the Sun.A few stars are less than a million years old.)

* Results may suggest that massive stars were born after the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud.

* Radiation-driven implosion may have triggered star formation.

'''QUESTION:''' HD 206267 formed 3 million years. Does the hot O star form first and then trigger star formation. Or are some YSOs formed nearby beforehand?

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T14:16:08Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? Do they measure a specific element characteristic? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation on filters and a picture here: http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Nakano 2012 Wide-Field Survey of Emission-line Stars in IC 1396 ==

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-17T14:11:47Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? How do they work? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? How are they different exactly? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

I found a good web explanation here:

http://en.wikipedia.org/wiki/Passband

[[File:Passband Filter Schematic.png]]

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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File:Passband Filter Schematic.png

2012-05-17T14:10:05Z

Bonadurer:

Summaries and questions on discussed papers

2012-05-16T19:24:56Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror) in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? How do they work? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? How are they different exactly? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-16T19:24:02Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? How do they work? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? How are they different exactly? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?

'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

This section 8.21 goes on to note:

While the effect of photoevaporation has been observed using direct imaging (so-called proplyd objects, O'dell et al.1993; O'dell & Wen 1994), a proof of triggered star formation is harder to obtain. Merely observing the presence of young stars in molecular clouds near hot stars is no solid evidence, because it is not clear whether the birth of the stars was triggered by the hot star, or whether stars were forming in these clouds regardless. Moreover, photoevaporation may act to disperse the circumstellar environment of protostars as a function of their distance, and therefore introduce an apparent evolutionary gradient which may incorrectly be interpreted as an age gradient (e.g. discussed by Beltr�an et al. 2009). The relatively simple nature of IC 1396, where the UV radiation field is dominated by the massive star system HD206267 (O6.5V), makes it a good region to study the influence of a hot star.

* They basically find that photoevaporation is perhaps only effective at removing disks within �1 pc from the radiation source and the age gradients prove true beyond that distance?

'''QUESTION:''' Can this be explained further? "The strongest argument in favour of triggered star formation comes from the dispersal of objects in front of (BRC) clouds A/B/E, shown close-up in Fig. 18. The clusters of our candidates in front of the ionized rims are significantly more dispersed than the embedded Class 0/I protostars inside the clouds, covering an area which is roughly 1 to 2 pc larger in diameter."

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-16T19:05:12Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

* INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain.
* The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? How do they work? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? How are they different exactly? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?
'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-16T19:04:13Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

* T Tauri star was discovered in 1852 to be a variable star.

* Today we know it is 100 million years old and 460 LY away.

* T Tauri stars were proposed to be YSOs in 1957.

'''QUESTION:''' What is the best way to describe any differences for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? How do they work? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? How are they different exactly? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?
'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-16T19:02:09Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

T Tauri star was discovered in 1852 to be a variable star.
Today we know it is 100 million years old and 460 LY away.
T Tauri stars were proposed to be YSOs in 1957.
QUESTION: Any other definitions for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? How do they work? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? How are they different exactly? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star. Study cites Choudhury 2010 and Getman 2007 in this regard.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?
'''GOOD SUMMARY on MASSIVE STARS--aka MOM STARS:'''
It is often claimed that radiation and stellar winds from O type stars may have a profound effect on nearby star formation. On one hand, a massive star may disrupt star formation by dispersing the local molecular cloud and removing circumstellar material from newly formed stars (UV photo-evaporation, e.g. Johnstone et al. 1998).

On the other hand, expanding ionization fronts may act to compress the gas around the periphery of an Hii region which then collapses to form stars (collect and collapse, Elmegreen & Lada 1977),or trigger star formation in a pre-existing cloud (e.g. radia-
tively driven implosion, Kessel-Deynet & Burkert 2003).

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

* Tripled the number of classical T Tauri stars compared to previous searches by Sicilia-Aguilar et al.
(2005, 2006a). 56 percent are at low masses and less than 500,000 years old.

'''QUESTION:''' In section 7.1 on Non-systematic uncertainties,what is the Monte Carlo approach? And Gaussian noise? How are they used to measure extinction?

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-16T18:45:19Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

T Tauri star was discovered in 1852 to be a variable star.
Today we know it is 100 million years old and 460 LY away.
T Tauri stars were proposed to be YSOs in 1957.
QUESTION: Any other definitions for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? How do they work? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? How are they different exactly? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:

* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?
'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock. The energy released in these shocks heats the infalling circumstellar gas, resulting in the
broad H� emission lines seen in classical T Tauri stars. This implies that the measured line luminosity LH� may be used to estimated the accretion luminosity and subsequently the mass accretion rate.

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

----

== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-16T18:38:47Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

T Tauri star was discovered in 1852 to be a variable star.
Today we know it is 100 million years old and 460 LY away.
T Tauri stars were proposed to be YSOs in 1957.
QUESTION: Any other definitions for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? How do they work? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? How are they different exactly? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:
* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star.

* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.

'''QUESTION:''' This is still debated, correct?
'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

* Telescope measured the ages, masses and radii of the young stars and from that concluded the mass accretion rates introduced by DeMarchi 2010.

'''COOL FACT:''' Mass accretion is thought to take place along magnetic field lines which act as channels connecting the
disc to the star. The infalling gas is essentially on a ballistic trajectory, falling on to the star at close to free-fall velocities,producing a hot impact shock.

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

----

=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
----

Summaries and questions on discussed papers

2012-05-16T18:34:25Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

----

== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

T Tauri star was discovered in 1852 to be a variable star.
Today we know it is 100 million years old and 460 LY away.
T Tauri stars were proposed to be YSOs in 1957.
QUESTION: Any other definitions for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.

'''QUESTIONS:''' What are the Sloan r' and i' filters exactly? How do they work? Are they different wavlengths--red and infrared? Does it help measure the infrared excess? How are they different exactly? E.g.; H Alpha wavelength is 656.28 nm when an electron orbit 3 falls 2nd orbit level.

'''QUESTION:''' Is this basically an optical (emission-line) study?

* Has data tables of 158 objects they think are young stars--out of one million objects.

* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.

* For target validation, it includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:
* Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star.
* Figure 9, page 11, is a great picture showing the hot big star (mother star) surrounded the young stars (all her baby stars). The infants are way out at the edge of the circle.
'''QUESTION:''' This is still debated, correct?
'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

----

== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

----

=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
----

Summaries and questions on discussed papers

2012-05-16T18:04:30Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

----

== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

T Tauri star was discovered in 1852 to be a variable star.
Today we know it is 100 million years old and 460 LY away.
T Tauri stars were proposed to be YSOs in 1957.
QUESTION: Any other definitions for T Tauri stars and YSOs?

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are located.
'''QUESTION:''' What is r and i--different wavlengths red and infrared? How are they different? H Alpha 656.28 nm when an electron orbit 3 falls 2nd orbit level.
* Has data tables of 158 objects they think are young stars;
* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.
* Also includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:
. Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star.
'''QUESTION:''' This is still debated, correct?

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

----
"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

----
''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

----
"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

----

== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

----

----

==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

----

== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-16T17:02:27Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

T Tauri star was discovered in 1852 to be a variable star.
Today we know it is 100 million years old and 460 LY away.
T Tauri stars were proposed to be YSOs in 1957.

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are locared.
'''QUESTION:''' What is r and i--red and infrared?
* Has data tables of 158 objects they think are young stars;
* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.
* Also includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:
. Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star.
'''QUESTION:''' This is still debated, correct?

'''COOL NOTE:''' Evidence suggests our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

----
"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

----
''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

----
"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

----

----

==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-16T17:01:58Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

T Tauri star was discovered in 1852 to be a variable star.
Today we know it is 100 million years old and 460 LY away.
T Tauri stars were proposed to be YSOs in 1957.

This study:

* Looked for T tauri candidates and accretion rates using IPHAS (r, i, Halpha); over the entire huge IC1396 complex where BRC 34 & 38 are locared.
'''QUESTION:''' What is r and i--red and infrared?
* Has data tables of 158 objects they think are young stars;
* C-WAYs need to incorporate what they found -- mainly brc 34 (cloud D) and 38 (cloud E), PREVIOUS SUMMARY: need to email these guys and ask for source lists at least in these regions.
* Also includes some 2 MASS and Spitzer data but only for T Tauri candidates, or possibly only in the center of the complex?

This study found:
. Evidence that the hot O star HD 206267 triggered star formation; find increasing accretion rates, disc excesses and younger ages as move away from the hot blue star.
'''QUESTION:''' This is still debated, correct?

'''COOL NOTE:''' Our Solar System formed near a massive star! (e.g. Hester & Desch 2005).

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

----

== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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Summaries and questions on discussed papers

2012-05-16T15:52:06Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

T Tauri star was discovered in 1852 to be a variable star. Today we know it is 100 million years old and 460 LY away.
T Tauri stars were proposed to be YSOs in 1957.

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

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"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

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''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

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== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

----

== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

----

== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

----

=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
----

Summaries and questions on discussed papers

2012-05-16T15:33:54Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

----

== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.

[[File:int_right.jpg]]
[[File:int_left.jpg]]

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

----
"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

----
''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

----
"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

----

== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

----

----

==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

----

== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

----

== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

----

== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

----

== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

----

=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
----

Summaries and questions on discussed papers

2012-05-16T15:27:58Z

Bonadurer: /* Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 */

----

== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope (100 inch mirror)in Canary Islands, Spain
The survey uses two broad-band filters and a narrow H-alpha filter to obtain deep images of nebulae in our Galaxy and for identifying rare types of stars.
[[File:int_right.JPG]][[File:int_left.JPG]]

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

----
"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

----
''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

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"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

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== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

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----

==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

----

== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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File:Int left.jpg

2012-05-16T15:24:44Z

Bonadurer:

File:Int right.jpg

2012-05-16T15:24:26Z

Bonadurer:

Summaries and questions on discussed papers

2012-05-16T15:20:00Z

Bonadurer: /* Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N */

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== Barensten 2011 T Tauri candidates and accretion rates using IPHAS:method and application to IC 1396 ==

INT is Isaac Newton Telescope in Canary Islands, Spain

== Getman 2006 X-Ray Study of Triggered Star Formation and Protostars in IC 1396N ==

An observation of IC 1396N with Chandra, so X-ray light. How long (total time) was the observation? 30 ks = 30 kilo seconds = 30,000 seconds = 500 min = 8.33 hours - '''Is this a long observation? I got the impression from the reading that it was short.'''

''Intro - What will be useful in this section for us?''

'''The cometary globule this study looks at is BRC 38?'''

Nice list of indicators of star formation in IC 1396N. Things we should know about

-IRAS source 21391 +5802

-H2O masers

-molecular outflows

-HH flows

-clusters of IR embedded sources

-radio mm portostars

Explanation of RDI - easy to understand.
Explanation of why an x-ray study - I was surprised. Didn't think about magnetic fields being active in YSO.

----
"2.1 - 2.3 Chandra Observation & Source List - The meat for us!"

The most important things here are the tables and figures. Locations given for the found sources and correlations to 2MASS. '''Will we eventually understand what each of these columns mean?'''

2.1 - Interesting that 8 corrections were made to the data. EIGHT pg 317-8
Data reduced to 117 point sources (listed in table 1); 66 of those correlated with 2MASS; 5 newly identified

----
''Sections 3, 4 & 5 - Interesting things about IC 1396N''

3.1-3.4 Data reduced to sources coming from star formation. 25 sources are probable members of the globule. Sources classified as class 0, I, II, III.

4.1- 4.3 It was interesting that there was flaring going on. '''Are YSO variable in the their light output, like a variable star?''' 4.3 was hard to understand. I have to sort out wavelengths and energies associated with each em light band.

5.1-5.3 Figure 10 a - This is a great picture of results of using different types of observations and even of resolution. Why correlation with other studies is needed.
Figure 10 c - Source 66 and 68 are so much brighter than the others. Interesting. It was also interesting that #66 is the brightest x-ray object in IC 1396N. '''What does it mean that it is 'one of the most heavily absorbed sources'?'''

Questions

1. Does this symbol mean of the Sun? M⊙ = mass in relation to the Sun?

2. What is IMF - initial mass function? pg 328, last full paragraph

3. What is MedE? pg 331 5.2

4. What is intervening column density? pg 332 5.3 2nd paragraph

5. What is extinction? pg 332 5.3 3rd paragraph

----
"Section 6 & 7 - Science questions and summary"

Section 6 pulls the info from the study into the larger science questions - What do these results say about triggered star formation and the two initiation methods mentioned? It seems that RDI (radiation driven implosion) is supported.

I like section 7's summary. Easy to understand and I like the list of classifications of the 25 YSO.

----

== Beltran 2009 The stellar population and complex structure of the bright-rimmed cloud IC 1396N ==

This article discusses the structure of this cloud and gives positions of everything it talks about. 18 pages worth of tables! Their conclusions are also different than the previous paper about star formation.

I found it interesting that individual sources we read about in the previous article have been resolved into several sources by the time this one was written.

Questions

1. They mention that bluer YSO mean older and redder are younger -- this is opposite of main sequence stars

2. '''What is on source images and off sources images? Why do you do this?''' this is to try and adjust for background light

The images went through 5 set of corrections or adjustments before photometry

3.2 The authors conclude not all star formation is triggered star formation in this cloud. Then what else is there?

3.3.1 All this info about H2 knots. Dense material. '''Does the red and blue shift indicate spinning?''' No, it is looking at a jet face on but not perpendicular

3.3.2 H2 flows are complicated. A lot of assumptions are made.

4. 736 sources found in all three bands - J, H K' 128 sources found only in HK' 67 sources found only in K' 79 sources found only in JH

Different conclusions from Getman. An age gradient is not found in the south-north direction of the globule; not all star formation in globule is by triggered star formation. NO alternative method given.

----

----

==Original SFO - Sugitani et al 1991==
Survey of BRCs to describe the BRCs themselves and look for YSOs. 
Palomar Sky Survey (PSS) and IRAS point sources. 

44 BRCs found in Palomar Sky survey prints that had associated IRAS point sources where all found to have IRAS point sources that were good candidates for being YSOs. Tables/images exist for; HII region locations, PPS finding charts, BRC location charts, IRAS point source properties (12, 25, 60, 100 micron), BRC and point source descriptions and plots. 

Questions to ask yourself as you read 

Abstract, Intro and Summary 
-what is the flow of all the types of nebulosity that they describe and the cause/effect relationship to star formation? 
-how will the understanding of this cause/effect help us in our closer study of just three BRCs? 

The Sample, Results 
-how did the authors take advantage of Palomar Sky Survey Prints? 
-how will this help future astronomers with their work? 
-table 3 lists exactly one IRAS source for each BRC, where are the rest of the YSOs we expect to see? 
Discussion 
Although 15 of the IRAS point sources were catagoized as type I and “really are” YSOs, why are all 44 of the sources considered good candidates for YSOs? 
==Most recent paper - Ogura et al 2002==
Looking for H-alpha emissions using grism spectroscopy to find previously undetected YSOs that do not have strong IR excess in order to collect more information on star formation in BRCs and contained HH objects, and further investigate small-scale sequential star formation (SSSSF). 
Optical (H-alpha using grism spectroscopy), 2 MASS 

Questions to ask yourself as you read 

Introduction, Observations and Data Reduction 
-why do the authors recommend higher resolution studies? 
-what is SSSSF and what is the evidence for supporting this hypothesis? 
-what is grism spectroscopy and how does it help “fill in some holes” in terms of YSOs? 
-how did the authors categorize H-alpha equivalent widths in “difficult cases”? Think about the usefulness of this data. 

Images and Data 
-what qualitative and quantitative information will be helpful to us in our study? List tables and images, highlighting information specific to our study. 
H-alpha stars, HH objects and Discussion 
-what did the authors find of interest in our particular BRCs? 
-what evidence is given to support further multi-wavelength studies searching for YSOs?

----

== Info to help you answer questions and things I just don't get ==

Data provided in 2002 paper - observation survey regions, dates, and exposure times; IRAS associated BRCs; H-alpha stars by BRC (BRC 27 (32 stars), 34 (2 stars), 38 (16 stars)), location, H-alpha EW, comments; H-alpha EW distribution; Finding charts (BRC 27 (chart k), 24 (chart o), 38 (chart q)); HH objects location and emission line intensities(BRC 38 only, 9 HH objects, data for 2); HH finding charts (BRC 38 only, chart d)

OB stars are hot, massive, short lived stars that emit enormous amounts of UV which ionizes surrounding interstellar gas forming HII regions and providing ionization/shock fronts to trigger star formation.
HII (H-two) regions are large, low-density clouds with large amounts of ionized atomic hydrogen and other gases. HII regions can be the birthplace of thousands of stars over millions of years until supernova explosions and stellar winds from massive stars disperse the remaining gas and leave behind a cluster (i.e. Pleiades).
Bok globules are dark dense clouds within HII regions, the result of formation of multiple star systems (can contain many young stars) that contain molecular hydrogen, carbon oxides, helium and silicate dust. Cometary globules are Bok globules that have comet like tail (can contain many young stars
BRCs (Bright Rimmed Clouds) are dense clumps of matter (can contain many young stars) in older HII regions which have been further compressed and illuminated and from which surrounding interstellar medium has been dispersed by UV radiation from nearby OB stars.
The hypothesis of small-scale sequential star formation (SSSSF) has redder stars in a BRC closer to the head of the BRC, furthest from the OB exciting star – stars are born as the shock wave moves away from the OB star, the youngest stars are the furthest from the OB star.
HH (Herbig-Haro) are short lived areas of emission nebulae from young stars (there are young stars nearby, possible still hidden in their cocoon), formed when material ejected from the poles of young stars collides with interstellar medium to produce visible light.
Hot Cirrus sources are filamentary (like cirrus clouds) structure that can be seen in the IR, but when “hot cirrus sources” are detected in an HII region, they may be YSOs that have been contaminated at the long wavelengths by emissions from the HII region.
Grism spectroscopy makes use of a prism/diffraction grating to allow light at a central wavelength to pass through. In this study a “wide H-alpha” of 6300-6750 angstroms was used.
???Author talks about JHK observations and two color diagrams, but I do not see data for this???

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== Spitzer Observations of IC 2118: “Witch Head Nebula” ==

Summary:

The Witch Head Nebula (WHN) is thought to be a site of triggered star formation. Observations in 7 IR bands using SST and 4 bands in optical yields IR excesses in 4 of 6 previously known T Tauri stars and discovery of 6 new candidate YSOs.

This article has a nice introduction that covers a bit of stellar formation overview due to 2 mechanisms: gravitational collapse and “triggered” from nearby events like supernova. The Initial Mass Function (IMF) and the star formation efficiency are supported by the inventory of YSOs formed in a cloud, which then supports closer study of the initial conditions of star formation.

A detailed comparison of the two formation mechanisms with respect to the IMF and stellar formation efficiency will assist with understanding the mechanics of star formation itself.

The data analysis section was highly detailed and technical. This section gave me the greatest comprehension challenge and also the greatest number of questions that require a bit more clarification.

The selection of YSO candidates focused on finding sources having an infrared excess characteristic of YSOs surrounded by a dust disk. A high source contamination rate was expected. Filtering mechanisms form the literature based on Spitzer colors were used to distinguish likely galaxies from likely members. Optical information was used to further winnow the candidate list.

Both color-color and color-magnitude diagrams from IRAC were used to select sources. 459 sources were identified having colors consistent with galaxies dominated by Polycyclic Aromatic Hydrocarbons (PAHs). 765 more sources having colors consistent with active galactic nuclei (AGN), only 27 sources are not flagged as background contaminants and have colors compatible with YSOs and with IRAC excess. The list of 27 sources not flagged as contaminants bears further scrutiny. 18 of the YSO candidates have magnitudes fainter than 12. As the brightness decreases, the probability of the object being background contamination increases.

The wealth of data allowed these data to additionally constrain the YSO selection. 18 faint sources all fall in the region occupied by main-sequence stars or background galaxies. The 9 remaining YSOs with magnitudes less than 12 all appear redder, near or above a 30 Myr isochrones. These are strongly suspected to be contaminants. The 9 brighter objects are included in the list of their (the authors) IRAC selected YSO candidates. There are restrictions imposed with the consequence that leads to a distance assumption that may be problematic. The details of this challenge appear in the bottom half of page 13 for further detailed description, should curiosity require investigation.

All 9 of the IRAC selected YSO candidates are seen at MIPS-24. There is a bit more technical justification about why seeing these candidates in MIPS-24 at one of the two distances proposed (~210 pc and ~440pc).

Most of the sources seen in the observations at 24 or 70 μm are foreground stars or background galaxies.

POSS and 2MASS and optical images for each candidate were used to verify that they did not appear extended in any of these bands. All YSO candidates passed the checks and appear to be point sources in all available bands.

The MIPS selection was technically detailed and the objects seemed to fall into either Class II or Class III with weak excesses. There appears to be three distinct groups of object: 1) objects of zero color (likely foreground or background stars), 2) objects that are faint and red (likely galaxies) and 3) objects that are bright and red (likely YSOs). There doesn’t appear to be any sources between the photospehric Class III and Class II objects. The chosen selection process may have gathered the YSO candidates into the group of brightest or reddest object, lending further support that the assertion of faint object being most likely background galaxies (bottom of page 14). Why is this so??

There is a good amount of detailed description of how the candidates were sorted out from the other sources. From the list of 10 YSO candidates, six are new discoveries. One of the Class II T Tauri stars is a flat disk. The fit for the edge-on-disk candidate was not the same as for the non-disk candidates, since the slope changes significantly depending on whether the MIPS points are included in the fit for the edge-on disk. I think I’d like to understand the slope correlation a bit better…

All of the YSO candidates are located in the head of the nebula, the most massive molecular cloud of the WHN. The distributions lend further support o the assertion that the IRAC and MIPS selected bright object are likely YSOs. The expected YSO candidates for the regions further south were not found. Apparently the conditions in this region do not support substantial star formation. The head of the nebula is about 3 times more massive than any of the other clouds.

There is a nice explanation of at least two intertwined mysteries that enshroud the WHN. The distance to it, and the external source that is responsible for the surface sculpture, illumination and possible trigger mechanism. There is a nice explanation of how the possible two sources (the Trapezium and Rigel) at different distances could solve the mysteries. There are arguments for both explanations, and the conclusion is that there is no clear answer. GAIA (galactic mapping mission proposed to launch in 2013) highlighted text abovecould provide a definitive answer by deriving accurate parallaxes to some objects.

The conclusion for the work states that the inventory of YSOs and candidates has doubles as a result of using Spitzer data to search for objects with IR excess in the region. SEDs are used extensively to identify YSO candidates. If the region is a triggered star formation mechanism, then trends of age or mass as they relate to location may be established. Since there are so few objects, since the distance is uncertain and since the spectral types for most of these objects is unknown, this correlation cannot be done rigorously.

Additional follow-up spectroscopic data are needed to confirm or refute the YSO status for the six new objects.

The new edge –on disk candidate in particular warrants further study, since such objects are relatively rare.

GAIA will be needed to resolve the mystery of the distance to the WHN.

Questions:

What:
1. I want to verify that I understand correctly that bands UVRcIc stand for: Ultraviolet, Visible, Red and Infrared, respectively.
2. Fat fielding issues
3. 100 MJy/ sr
4. Median boxcar filter
5. NaNs
6. UV RcIc
7. “real matches “
8. false source associations
9. centroiding
10. ELAIS
11. U and 70 micro meters
12. Optical Mv
13. VLBA and VLBI
14. mas/yr

How and HUH? : - see text above as well…

1. APEXZ portion of MOPEX
2. Zero point used to convert flux densities to magnitudes
3. …as a final check on our measurements.
4. …through observation of Landolt standards… Does this mean that the additional epoc was just for verification of data integrity?
5. …deviate significantly from zero
Why?
1. The data were further processed…
2. …we wished to add reddened stellar models to the plots…

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== New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE ==
New Young Star Candidates in the Taurus-Auriga Region as Selected from WISE

Summary: WISE data is used to search for YSO candidates in Taurus from a 260 square degree patch of sky to encompass previously identified Taurus members. Near and mid IR colors are used to select objects with apparent IR excesses and incorporate other catalogs of ancillary data. There is likely to be contamination lingering in this candidate list, and follow up spectra are warranted.

Even though Spitzer is good at finding new young stars, some are located surprisingly far from the traditional location based on CO gas or IRAS dust maps. A 44 square degree survey of Taurus was done with Spitzer. It was found that any solely near and mid IR color selection was filled with contamination from galaxies and asymptotic giant brand (AGB) stars. The use of ancillary data was crucial to establishing a list of high quality new members of Taurus. WISE surveyed the entire sky; the depth of coverage in the Taurus region is somewhat degraded relative to regions of comparable ecliptic latitude due to Moon avoidance maneuvers. Since the cloud is only 140 pc away, both surveys (Spitzer and WISE) should easily detect legitimate Taurus members.

New Taurus candidates were selected with IR excesses using WISE colors with the Koenig et al method. There are three lists: 1) recovered young stars, 2) rejected objects, and 3) candidate new Taurus members.

A substantial multi-wavelength database was assembled for point sources throughout the Taurus region. Not every source has photometry at all bands due to variations in depth and spatial coverage among the surveys involved.

The WISE data acquisition and reduction are discussed in Wright et al, Jarrett et al and in the Explanatory Supplement to the WISE preliminary Data Release Products. Any sources with contamination and confusion flags were rejected, as were “DHOP” (what’s this?) characters.

There were about 2.38 MILLION sources. Signal to Noise Ratio (SNR) measurements were used to drastically shrink the catalog to about 7,000 sources. The SNR cut was used in W4 to limit the contamination. Since the contamination rate for any color selection is expected to be relatively large, ancillary data are crucial for culling the list to high - quality candidates. A rough total of about 2,000 contaminants per square degree were determined. Approximately 1,760 YSO candidates were obtained before imposing additional requirements (which were???) to the SNR be imposed on all four WISE channels reduced the number to 1,014.

Ancillary data were used to weed out contaminants from the list of potential YSO candidates. Only 27 sources on the list of potential YSOs found matches with SDSS spectra.

Of the 1,014 potential YSOs, 196 of them have matches to previously identified stars. 18 of these are listed as unconfirmed candidates in Rebull et al (2010).

Manual Inspection was used to sort objects into “likely contaminant” or “perhaps YSO” bins. The four criteria used to categorize were: 1) matching objects in SIMBAD, 2) matches to objects identified as contaminants in Rebull at al (2010), 3) matches to the 2MASS Extended Source Catalog, and 4) identification as extended in the SDSS pipeline. SEDs were then generated using all the photometric date in the database, and the SEDs were inspected. Based on experience, the SEDs were then categorized as still possible YSO candidates, or likely extragalactic objects. This process may have dropped viable YSO candidates similar to MHO-1 (huh?) or Haro 6-39 (huh?). This process left about 130 candidates. The sources were identified as either being likely subjected to source contamination (HOW?) resolved as a likely galaxy (HOW?) or still apparently clean, point sources (HOW?) This brought the number of candidates down to about 94 objects. All SEDs for the 94 appear in the Appendix.

Projected location of the previously identified YSOs is generally highly clustered along the filamentary distribution of gas and dust, and the new objects are less clustered. The goal was to look for new YSOs outside the canonical groupings of previously known Taurus members. This could also be an indication of persistent contamination in the surviving list of YSOs candidates. There is more discussion about the location of previously identified YSOs and contaminants.

Previous YSOs are generally found in regions of high Av, and background galaxies are found in regions of low Av. The new objects are not particularly clustered, but not evenly distributed either. Most of the previously identified YSOs are bright and most of the contaminants are faint. The new YSO candidates span the range of bright and faint.

The list of objects by type: recovery of 196 previously identified young stars with IR excess, 686 likely to be galaxies, 13 foreground stars, 1 planetary nebula, 24 objects that are likely to be confusing and 94 new YSO candidates that are widely distributed in space.

Questions:

1. What s the “J” in 2MASS J04360131
2. What is color near zero?
3. What is the reddening factor?
4. What is the meaning of “...in the right regime for JHKs diagram”
5. What is “z measurement”?
6. What are large inner disk holes?

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== New Young Star Candidates in CG4 and Sa101 ==

The introduction to this paper also has some very good background about the Gum Nebula and the stellar formation mechanisms thought to apply within it. Previous studies by Reipurth and Pettersson are summarized, with a conclusion that stars associated with the Cometary Globule 4 (CG4) and Sa 101 are associated with the Gum Nebula. The distances to all considered objects are uncertain; the distances vary from 300 to 500 pc. The extrema of the distance estimates were tested, though the results are not strongly dependent on distance. The region contains previously identified young stars, so it is likely that there are more young stars of lower mass or more embedded than those previously discovered.

The data sections, like the other two papers summarized, are highly technical and summarizing all the details doesn’t seem fruitful beyond this very minimal overview. More detailed reading should be the way to get more detail about the data analysis.

For the IRAC data, two exposures were taken with three dithers per position. The two observational locations were reduced independently even though they overlap on the sky. Some of the very bright stars in the filed of view had instrumental effects that rendered the data very difficult to work with. There is quite a bit of detailed description of calibration technique, correlation and photometry and error reduction methods.

The MIPS 24 and 70 micron data were combined. The 24-micron data were affected by the bright objects and required additional processing. The background levels between the two observations were problematic, and a description of how this was addressed was discussed. Optimized data reduction to obtain brighter source measurements led to many sources fainter than the bright sources in the image being excluded from the catalog because the scientific goals are aimed at brighter objects. There is a good, technical justification of the filtering choices made to process the data.

The optical data used the observed Landolt (1992) standard stars of two or three fields several times per night for photometric calibration. For each target, aperture photometry was performed using multiple size apertures. There is a discussion of the correction used for a noticeable variation of the point-spread function (PSF) that is location dependent on the CCD.

The bandmerging of the photometric data was first merged from all four IRAC channels with the near IR 2MASS data for each observation. This was then merged together with the source lists from each observation. The MIPS data was then included, and then the optical data was merged. A very detailed discussion of how this was done follows.

YSO candidate properties are discussed in the subset of optical, near IR, B-band and SEDs. Optical data can greatly aid in the confirmation or refutation of YSO candidacy because they provide constraints on the Wien side of the SED. Objects with optical data that have already been ruled out as SOs based on the IRAC properties are all well below the 30 Myr isochrones scaled to 500 pc. Deeper optical data are desirable to obtain magnitude estimates for the remaining YSO candidates. The degree of reddening is difficult to estimate because the spectral types for most of the sources are not available. The candidates have infrared excess with a moderate degree of reddening. Young stars that are actively accreting from their circumstellar disks can have excess UV emission in the U or B bands or longer. These bands are also the most sensitive to reddening. Figure 13 is discussed with respect to mass accretion. The coordinates of the YSOs are listed in Table 1. The SEDs of the 22 YSO candidates are displayed in figures 14 - 16. A spectral type of MO was assumed for the remaining objects. A redden model of each object is shown and normalized to the Ks band where possible. These are presented as a guide to the eye rather than a robust fit to the object to allow the immediate IR excesses to be immediately apparent. There is quite a bit of more technically detailed description of the properties in the SEDs section than is summarized here.

There is a galaxy, ESO 257 – G 019 that is mentioned because it appears in the observation field. It has not been studied, and some basic astrometric data about it is listed.

In conclusion, 6 previously identified young stars were rediscovered. There are 16 new YSOs that were discovered and evaluated with ground-based data in the near IR from 2MASS to constrain the SEDs of the candidates. The new young star candidates were graded into confidence groups. Additional data will be needed, such as optical photometry where it is missing and optical spectroscopy to obtain spectral types.

I didn’t have any questions about this article.

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=="Triggered Star Formation and Evolution of T-Tauri Stars in and Around Bright-Rimmed Clouds" by Chauhan, et al. and "Triggered Star Formation and Young Stellar Population in Bright-Rimmed Cloud SFO 38" by Choudhury, et al.==

[[File:Chauhan et al Reading Guide.pdf]]

[[File:Choudhury Guided Reading.pdf]]
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C-WAYS Summer visit logistics

2012-04-30T19:35:19Z

Bonadurer: /* Software to install */

I sent out a "big travel document" in March. It has all the information you need re: flights, etc. I will send it again in April or the beginning of May as a reminder.

It will reference [http://coolcosmos.ipac.caltech.edu/cosmic_classroom/teacher_research/visit/ this page] on the CoolCosmos website. This is where you find the legal things, like the student forms.

=High-level schedule=

The work days we've agreed upon are Jul 9-12, where there will be minimal help from me on Jul 12 as sort of a "training run" for when you go home.

I propose you come in relatively early on Jul 8, and plan on doing dinner at my house that night.

*Sunday morning/early afternoon - arrive in LA
*Sunday night - pizza party at Luisa's ... pizza arrives at 6. come by 5 or 5:30 if you want to play with Andrew!
*Monday morning 8:30-12? - lectures
*Monday afternoon 1-5 - software setup. WISE archive workthrough. Start to work with mosaics.
*Tuesday all day - hands-on work with computers
*Wednesday morning?? - JPL tour
*Wednesday afternoon - wrapup, plan for when you go home
*Thursday morning - Work on your own or small groups. Try to do some of the tasks we did as a group. Compare notes. Can you work on your own at home without me?
*Thursday afternoon - Reconvene for questions and help.
*Friday - return home

TO BE SCHEDULED - WHEN TO LEARN ABOUT THE LCOGT TELESCOPES.

=Software to install=

Make sure you (and all your students who are coming) '''each''' have a '''functional laptop''' that you know how to use with as much of the relevant software installed as possible well before you get on the plane. Trust me. Makes it '''much''' easier if you do all this ahead of time, including starting it up to make sure it works.
*[http://hea-www.harvard.edu/RD/ds9/ ds9]
*[http://spider.ipac.caltech.edu/staff/laher/apt/ APT]
*a web browser (Firefox, Safari, or Google Chrome -- NOT MICROSOFT INTERNET EXPLORER)
*Excel or other spreadsheet program (Google Docs is ok if your school lets you access it; most of the rest of us will be working with various versions of Excel)

Please list your version of Microsoft Office in this table
{| border="1"
|'''Name'''
|'''Microsoft Office version'''
|'''or Microsoft Excell if you don't have the whole suite'''
|-
|Peggy
|2003, 2007, 2010
|
|-
|Jackie
|
|
|-
|Lauren
|
|
|-
|Debbie
|2003, 2010 (preferred version)
|
|-
|Bob
|2007 at work. 2010 at home.
|
|-
|J.D.
|
|
|-
|Mark
|
|
|-
|Russ
|
|
|-
|Babar
|
|
|-
|Luisa
| 2008 on the desktop, 2011 on the laptop (which is what you'll see when i hook it up to the projector). NB: they are both Macs!
|
|-
|
|
|
|-
|
|
|}

'''Also''' make sure you have all the passwords you need for installing new software, getting on a wireless network, or getting back into your machine if it reboots.

Besides the computer, you will need something to write on and something to write with to take notes! Experience has shown that this should be more than post-it notes. I will give you handouts, so the hyperorganized among you may want, e.g., a 3-ring binder.

=Flight & student & housing details=

''TO COME....''

Bob BRC 34

2012-03-05T21:45:31Z

Bonadurer: /* Location of BRC 34 */

==Location of BRC 34==
As a Planetarium teacher, I wanted to know where BRC 34 was located in the sky. What constellation it was in? (Cepheus the King) What was the nearest bright star? (Alderamin & Deneb)

The image below was created using Starry Night software and Paint.

[[File:Elephant_Trunk_Nebula_Location S.JPG]]

Below is a picture of the locations of BRC 34 & 38 in IC 1396--the Elephant Trunk Nebula. I am not 100 percent sure if I got the positions correct. If anyone can double check that would be helpful.

It is curious to see the 38's brighter rim compared to 34's.

The picture comes from the Astronomy Picture of the Day http://apod.nasa.gov/apod/ap110425.html
Credit & Copyright: Geert Barentsen & Jorick Vink (Armagh Observatory) & the IPHAS Collaboration

[[File:BRC_34_&_38_Locations S.JPG]]

==BRC 34 FINDINGS==

From last year’s NITARP team proposal we have the following information on BRC 34.

'''''Sugitani (1991)'''''

LOCATION: RA 21h 32m 51.2s DEC +58d 08m 43s

DISTANCE: 0.75 kilo parsecs or 2,400 light years

CLASSIFICATION: Type A BRC

'''''Ogura (2002)'''''

STARS: Found two Hα emission stars found in BRC 34.

'''Morgan (2004)'''

Defined the boundary layer of BRC 34. No 20-cm emission was associated with the rim of BRC 34. They used archival data from IRAS, NRAO/VLA Sky Survey
(NVSS), Digitized Sky Survey (DSS) and the mid-course Space experiment (MSX).

'''Valdettaro et al. (2005)'''

Did not detect water maser emissions indicative of YSOs at 22.2 GHz. They surmised that the negative results were due to the emission from the heated dust near the head of the BRC. This might also be indicative of low-mass star formation.

'''Morgan et al. (2008)'''

Found that BRC 34 did not include any T-Tauri stars nor any class I YSO candidates. They proposed that the lack of YSOs might be due to the protostellar core being at the early stages of evolution. They used SCUBA data and supplemented their findings with NASA/IPAC Infrared Science Archive data – IRAS at 12, 25, 60 and 100 μm and Two-Millimeter All-Sky Survey (2MASS) at JHKs bands. A search of the 2MASS catalog by Morgan (2008)

'''Morgan et al.(2009)'''

Eliminated BRC 34 as a good candidate for radiation driven implosion and suggested its evolution would not be affected by nearby OB stars. They used CO spectra and previous work to obtain this conclusion.

==FURTHER RESULTS for BRC 34==

'''Barensten (2011)'''

BRC 34 is defined as bright-rimmed cloud D. Though this study tripled the number (158) of classical T Tauri candidates in the IC 1396 region, most were found by bright-rimmed clouds A/B and E (BRC 38). According to Figure 9 in their study, no candidates were found near BRC 34.

Other results revealed that 56 per cent of the candidates below 0.5M—or low mass stars. Found strong indication that the formation of these clusters has been sequentially triggered by the massive star HD 206267.

'''Johnson 2012'''

This study from last year’s NITARP team found 8 new candidates for YSOs in BRC 34. There was one known before their study. Most of these YSOs (6) were classified in the flat class.

'''Saurin 2012'''

There is no direct mention of BRC 34 here, though it was studied. Indirectly we might conclude that BRC 34 has a lower central density, suggesting even smaller star clusters(?) based on the study’s finding that “BRC33, BRC36, BRC37, BRC38 and BRC39 have profiles with relatively high central density, suggesting small star clusters.”

'''Nagano 2012'''

Again, this paper did not find much activity in BRC 34 though it does state, “Some Hα stars appear to be associated with other small bright rimmed clouds such as Rim C and SFO 34 (Rim D).”

It adds though, “ total of 639 Hα emission-line stars were detected in an area of 4.2 deg2 and their i′-photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267, which is the main exciting star of the H ii region.”

==CONCLUSION==

The 2011 proposal concluded with “we will investigate the properties of this object (BRC 34) with Spitzer archival data, and compare the number of YSO candidates found here with our other target, BRC 27. The literature suggests that we will find fewer YSO candidates here than in BRC 27.

The latest research seems to suggest that this will be the case for our study in 2012--although does the WISE data in anyway suggest a different conclusion?

==Historical Narrative of IC 1396==

I just found this an interesting take on the region that contains BRC 34 & 38. From the website: (http://www.robgendlerastropics.com/IC1396text.html)

IC 1396 is a large HII region in the constellation Cepheus spanning 3 full degrees of winter sky, the same angular distance of 6 full moons. It formed at the southern edge of an enormous 400 light year bubble of molecular gas known as the Cepheus bubble. Amazingly the IC 1396 complex is illuminated by a single massive star, the class O6 star HD206267, a blue supergiant located in the center of the donut shaped emission cloud. HD206267 is member of the cluster, known as Trumpler 37, believed to be the core of the expansive Cepheus OB2 association. HD206267 is a trapezium type stellar system with HD206267 as the dominant ultraviolet energy source with a smaller UV contribution from three cooler companion B0 type stars. The stars of the entire trumpler 37 cluster are about 7 million years old, although HD206267 formed more recently about 4 million years ago.
A distinct feature of IC1396 is the radial arrangement of several bright rimmed globules that form a loose and slowly expanding ring around the illuminating stars. The ring of loosely arranged dark globules has a radius of about 40 light years with HD206267 at its center. The "comet-like" configuration of some of these dark structures has coined the descriptive term "cometary globule". Although several of the globules are optically conspicuous the most prominent is catalogued as IC 1396A. IC 1396A contains the well known reflection nebula vdB 142. Low and intermediate mass stars appear to be actively forming within the globules. The star formation within the globules has been induced by a process known as "radiation driven implosion" where the ultraviolet flux from a massive star like HD206267 compresses the cold molecular gas within the globules, thus triggering collapse of the cloud and subsequent formation of lower mass stars.

Attempts to trace the history of IC 1396 point to a complex interplay of equentially triggered star formation and cloud-cloud interactions. Events likely unfolded with an initial burst of star formation that occurred between 13 and 18 million years ago and gave rise to the first generation of stars which includes the existing nearby cluster NGC 7160. The more massive members from that first generation of stars went on to destroy themselves in supernovae explosions and no longer exist today. About 7 to 8 million years ago the effects of the first generation of supernova driven shock fronts and powerful stellar winds from existing stars created a huge 400 light year diameter bubble known as the Cepheus bubble. The expanding bubble compressed and flattened surrounding molecular clouds triggering a second burst of star formation which went on to form the Cepheus OB2 association some 7 million years ago. Also formed in this second generation of star formation were Trumpler 37 and its dominant star, HD206267 some 4 million years ago. Under the influence of the ionizing radiation field from the new star cluster, the HII cloud IC 1396 and its globules formed some 2 to 3 million years ago. Triggered by the expanding Cepheus bubble many well known HII regions have formed along its perimeter including IC 1396, Sh2-129, 133, 134, and 140. As IC 1396 expanded from the stellar winds of HD206267, surviving fragments of molecular clouds in the form of globules formed into an expanding ring around the central exciting star. The third and youngest generation of lower mass stars is currently forming within the dark globules of IC 1396 by the process of radiation driven implosion.

The bright yellow star just to the north of IC1396 is the supergiant mu cephei. It formed during the first generation of stars which created the Cepheus bubble. It has the distinction of being one of the most luminous stars in our galaxy, emitting 350,000 times the power of our sun.

File:Sky Map for BRC 27 Location.jpg

2012-02-27T20:34:19Z

Bonadurer:

File:Seagull Nebula Ebers.JPG

2012-02-27T20:24:47Z

Bonadurer:

File:BRC 27 Location.jpg

2012-02-27T20:07:45Z

Bonadurer: uploaded a new version of "File:BRC 27 Location.jpg"

File:BRC 27 Location.jpg

2012-02-27T20:07:16Z

Bonadurer: uploaded a new version of "File:BRC 27 Location.jpg": Reverted to version as of 20:04, 27 February 2012

File:BRC 27 Location.jpg

2012-02-27T20:05:31Z

Bonadurer: uploaded a new version of "File:BRC 27 Location.jpg": Reverted to version as of 20:02, 27 February 2012

File:BRC 27 Location.jpg

2012-02-27T20:05:18Z

Bonadurer: uploaded a new version of "File:BRC 27 Location.jpg": Reverted to version as of 20:02, 27 February 2012

File:BRC 27 Location.jpg

2012-02-27T20:04:55Z

Bonadurer: uploaded a new version of "File:BRC 27 Location.jpg"

File:BRC 27 Location.jpg

2012-02-27T20:02:19Z

Bonadurer:

Jackie BRC 38

2012-02-27T17:18:53Z

Bonadurer: /* Articles */

==Location of BRC 38==
I need a picture in my head. I found these helpful. The first is the one Luisa already put up. The 2nd is from APOD (http://apod.nasa.gov/apod/ap110425.html). The 3rd is from Getman et al. 2006 

[[image:tr37where.png|250px]] [[image:brc38.png | 250px]][[image:brc_38_Getman2006paper.png|300px]]

== Information about BRC 38==
Bright Rimmed Cloud 38 in IC 1396. Since it is located in the north part of IC 1396 is it often referred to as IC 1396N. 
It has a C shape with the southern edge as the brightest part (Pottasch et al. 1956). 
Location with intermediate mass protostars, though some (Ogura & Sugitani 1999) suggest there is probably a lot of low mass formation going on too. Wang et al. 2009 believes potential for high mass stars forming here also. 
H2 jets found (Saraceno et al. 1996; Nisini et al. 2001) 
Herbig-Haro objects found (Repurth et al. 2003 
Observed in many wavelengths - it would be good to get the specific wavelengths in each band
: optical (IPHAS, several optical - including Yerkes in the 1950s - coming from Chicago I have to cheer!!),
: infrared (2MASS,
: radio (IRAM & BIMA)
: x-ray
 
==Draft Proposal==
1. What is the structure of brc 38? - classification of cloud (type A I believe) & why; H2 jets and Herbig-Haro objects & what they indicate; 
2. What is the distance of the brc?

3. What is known about YSO in this region - this might be H alpha emission stars (??); 
a. How many have been found with what kind of detection (type of detector - X-ray, infrared, visible, etc); 
b. What kind (low mass, intermediate, high mass); 
c. Where in the brc are YSO located? 
d. What kind of formation process is indicated - triggered or collapse? 

4. What do we expect to find in this section? 

== Questions ==
I am sure there are a lot more!! After fooling around with wiki editing, this is all that is left in my head at present.

1. One IRAS (Infrared Astronomical Satellite) location (IRAS 21391+5802) seems to be the central point or at least this location that keeps coming up. What is this? 
2. LWS spectrum - is this as simple as long wavelength? 
3. Still unclear on what exactly the following are. I have looked them up but they are not clear in my head - maser, Herbig-Haro objects, FIR colors, MIP colors 
4. When we talk about BRC 38, are we talking about the whole C rim and globular area it half encircles? Where does the IRAS source 21391+5802 fit in our picture? 
5. Is submillimeter wavelengths (SUBA) infrared or microwave? 
6. Is HD 206267 affecting the whole region with its radiation? 

== Search phrases ==
*BRC 38
*sfo 38
*21:40:42+52:16:13
*21391+5802
*IC 1396N
*Cepheus OB2
*IMYSO

== Articles ==

{| {{table}}
{| border="1"
| align="center" style="background:#f0f0f0;"|'''Author Date'''
| align="center" style="background:#f0f0f0;"|'''Article Title'''
| align="center" style="background:#f0f0f0;"|'''Comments'''
| align="center" style="background:#f0f0f0;"|'''URL'''

|-
| 1a. Nagano et al. 2012 ||Wide Field Survey of Emission-line Stars in IC 1396||Nagano reports a total of 639 Hα emission-line stars were detected in an area of 4.2 deg2 and their i′-photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267, which is the main exciting star of the H ii region.” || [[Media:Nagano_2012.pdf]]

|-
| 1b. saurin et al. 2012 ||the embedded cluster or assoiciation trumpter 37 in ir 1396||'''Luisa adds:''' no individual data tables to use; they are interested in statistical properties of the regions. good 'big picture' kind of thing, but no real use for us in terms of our specific project. '''Peggy adds:''' 2MASS observations of BRC 38, Primary focus Trumpler 37, but analyzed 2Mass photometry of 11 BRCs in IC 1396 including BRC 38. All associated with IRAS sources (prob protostars) massive nearby star HR 8281 may have triggered sequential star formation via winds and UV. Photometric errors </= 0.1 mag removed for stars less than 0.5 arcmin radius for BRC 38 b/c high absorption? Relatively high central densities = small star clusters. Getman et al 2007 found sequential star formation evidence for BRC 38, spatial gradient stellar age in direction to triggering star as well as YSOs. BRC 38 stellar mass of ~15Mo assumed representative of area. Lists ra/dec, angular and linear dist to HR 8281 --Peggy Piper 12:23, 21 February 2012 (PST) ||http://arxiv.org/pdf/1201.2704.pdf
|-
| 2.. Barensten et al. 2011||T tauri candidates and accretion rates using IPHAS: method and application to IC 1396||'''Luisa adds:''' YES this is a useful paper. data tables of objects they think are young. their shortlist may or may not overlap with the fields we care about in brc 34 and 38, but still very useful to include. if, when we get to that point of needing these objects, they still haven't released the full IPHAS catalog, i will email these guys and ask for source lists in the regions we care about (34 and 38) '''Peggy adds:''' Includes BRC 38 which is called cloud E; Looking for YSOs in all of 1396; list 158 candidates; uses IPHAS survey data - Halpha, r, I filters on isaac newton telescope Specifically looking for T Tauri through Halpha emissions. Also includes 2 MASS and Spitzer data but only for T Tauri candidates? Find increasing accretion rates, disc excesses and younger ages as move away from HD 206267 towards Cloud A (BRC 38 is Cloud E)--Peggy Piper 12:47, 21 February 2012 (PST) ||http://arxiv.org/pdf/1103.1646v1.pdf
|-
| 3. choudhury et al. 2010||Triggered star formation and YSO population in Bright Rimmed SRO 38||'''Luisa adds:''' YES this is useful, if for no other reason than they used the Spitzer data. they definitely have data tables too. 44 YSOs identified in brc 38 - evidence for radiation driven implosion (RDI); spitzer IRAC & MIPS data, optical BVRI ||http://arxiv.org/pdf/1005.1841v1.pdf
|-
| Morgan et al. 2010||Ammonia observations of bright-rimmed clouds: establishing a sample of triggered protostars||'''Luisa adds:''' Radio. ignore at least for now Radio observations (Green Bank) of brcs; furthering earlier work of morgan, confirming brc is triggered star formation site ||http://arxiv.org/pdf/1006.0833v1.pdf
|-
| Crimier et al. 2010||Physical structure of the envelopes of intermediate-mass protostars||'''Luisa adds''': too theoretical. ignore. a study that says that the mass of the final star of a protostar is linked to the mass of the envelope around the protostar, not the density of the parent cloud - backbground on IM protostars??||http://arxiv.org/pdf/1005.0947v1.pdf
|-
| Ogura 2010||Triggered star formation assoicated with HII regions||'''Luisa adds''': overview. conference proceedings. meat of this analysis already in other journal articles, i am pretty sure. ignore for now. Not really about BRC 38 but discusses curent state of triggered star formation theory||[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?2010ASInC...1...19O&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf ASI Conference Series, 2010, Vol 1, pp 19-25]
|-
| 4. beltran et al. 2009||The stellar population and complex structure of the bright-rimmed cloud ic 1396N||'''Luisa adds''': YES very useful! A study through JHK filters; 736 sources found in all 3 bands (filters); h2 emission shows jet like structure||http://arxiv.org/pdf/0902.4543v1.pdf
|-
| Morgan L. K., Urquhart J. S., Thompson M. A., 2009 ON LAST YEAR'S LIST||CO observations towards bright-rimmed clouds||'''Luisa adds:''' Radio. ignore at least for now Luisa's old notes: JCMT (CO) observations. both 27 and 34 in here. 22 arcsec resolution! (see Resolution and their fig 2 here.) Likely last of his thesis, or first of his postdoc. (Look, his address changed, so this was published while he was a postdoc, but it's the same collaborators as before at his old institution, so my guess it's leftover thesis work.) They think 27 has been triggered, 34 not; this provides a nice compare-and-contrast opportunity for our write-up. Quick read.||[http://cdsbib.u-strasbg.fr/cgi-bin/cdsbib?2009MNRAS.400.1726M 2009, MNRAS, 400, 1726]
|-
| 5. fuente et al. 2009||Dissecting an intermediate-mass (IM) prostar||'''luisa adds:''' hm. very narrowly focused paper, seems to be just on one object and radio. was ready to say ignore it, but it is probably worth a quick skim to see if they mention anything substantive about the 'YSO BIMA 3' and 'cluster BIMA 2' mentioned in the abstract. A look at IRAS 21391+5802 emissions of N2H+, CH3CN, CS, BIMA (1.2mm & 3.1mm)||http://arxiv.org/pdf/0909.2267v1.pdf
|-
| Wang et al. 2009||The relation between 13CO j=2-1 line width in moelcular clouds and bolometric luminosity of associated IRAS sources||'''Luisa adds:''' Radio. ignore at least for now IRAS 21391+5802 - suggests that it is a star forming cluster where high-mass stars will form||http://arxiv.org/pdf/0909.3312v1.pdf
|-
| 6. Chauhan et al. 2009 ON LAST YEAR'S LIST||Triggered star formation & evolution of t-tauri stars in and around BRC||'''Luisa adds:''' YES this is a useful paper -- they are using JHK to select YSOs and including IRAC (but not MIPS) in their assessment of youth. we will be using longer-wavelength infrared to find the objects, so we will find a different set of objects. (ps they also didn't do that hot a job with source matching to the literature. we can do better.) Study that looked at ages of star forming clusters. Seems to have a lot of background material on BRC 38 ||[http://arxiv.org/pdf/0903.2122v1.pdf 2009, MNRAS, 396, 964]
|-
| Morgan et al. 2007 ON LAST YEAR'S LIST||A scuba survey of BRC||'''Luisa adds:''' Radio. ignore at least for now BRC 38 included in this study with SUBA data (submillimeter - microwave??); Luisa's notes: SCUBA submm survey (450+850 um) plus IRAS (12, 25, 60, 100 um), MSX, and 2MASS (erroneously identified as 2mm but really 2 micron). both 27 and 34 in here. next part of a PhD thesis. lots of nice overview, summary (as would be expected for a thesis) spread throughout article. seems to be a really long paper, but is almost all figures in the appendix. relevant issues: how the objects they are talking about (at long and short wavelengths) compare to what we see in our images (see Resolution and their, e.g., fig 4). Forward reference to Spitzer data analysis like ours but then says have already looked for GLIMPSE, 24 um obs. They are only looking at low-res flux densities. Appendix may be useful for scavenging additional targets if we want to do more analysis on more targets.||[http://arxiv.org/pdf/0711.0775v1.pdf 2008, A&A, 477, 557]
|-
| Neri et al. 2007||The IC 1396N proto-cluster at a scale of ~250 AU||'''Luisa adds:''' radio. ignore for now at least. observations in millimeter range to help develop understanding of formation of clusters vs individual star formation||http://arxiv.org/pdf/0705.2663v1.pdf
|-
| 7. Getman et al. 2007||X-ray study of triggered star formation and protostars in IC 1396N||'''Luisa adds:''' YES this is useful x-ray sources in the globule of ic 1396N; good pictures to help with the visualization of 1396N and these sources; evidence of sequential star formation||http://arxiv.org/pdf/astro-ph/0607006v2.pdf
|-
| Patel et al. 2007||Submillimeter array observations of 321 ghz water maser emission in cepheus a||'''Luisa adds:''' Radio. ignore at least for now No don\'t think there is anything here||http://arxiv.org/pdf/astro-ph/0702696v1.pdf
|-
| 8. Connelley et al. 2006||Infrared Nebulae around Young stellar objects||'''Luisa adds:''' check this to see if there is anything point source-y in here. IRAS 21391+5802 - images show jet-like nebula and large patches of nebulosity||http://arxiv.org/pdf/astro-ph/0611634v1.pdf
|-
| Valdettaro et al. 2005 ON LAST YEAR'S LIST||h2o maser emission from bright rimmed clouds in the northern hemisphere||'''Luisa adds:''' Radio. ignore at least for now H2O maser studied in brc 38; points to paper Valdettaro et al. 2005b which is supposed to be about analysis of BRC 38. Luisa's old notes: 22.2 GHz (=1.35 cm if I did my math right). Really nice intro summarizing the big picture. Following up on Morgan and similar work asserting high-mass stars forming in BRCs by looking for masers. Our objects observed, not detected. Finding lots of non-detections, suggesting that low-mass stars forming instead. Nice, short writeup of basically a non-result, and I think they've gotten the interpretation spot-on. ||[http://arxiv.org/pdf/astro-ph/0508446v1.pdf 2005, A&A, 443, 535]
|-
| Beltran et al. 2004||The dense moelcular cores in IRAS 21391 +5802 region||'''Luisa adds:''' Radio and it sounds like theoretical models. ignore. Three sources found with BIMA (??) observations in 21391+5802; Hard to read as they are trying to use data to fit/model how gas is emitted from the core||http://arxiv.org/pdf/astro-ph/0407102v1.pdf
|-
| 9. Reipurth et al. 2003||Blowout from IC 1396N: The emergence of Herbig-Haro objects in the vicinity of bright-rimmed clouds||'''Luisa adds:''' Reipurth et al usually work in Ha or forbidden emission lines to find HH objects. look to see if they have a list of objects in the region we care about, or if this is a more general paper. Herbig-Haro flow (HH 777) found coming out of ic 1396N; located at 214041.6+581638 (in IR, I think)||[http://iopscience.iop.org/1538-4357/593/1/L47/pdf/17405.web.pdf 2002, ApJ, 123:2597-2626]
|-
| 10. Ogura, et el 2002 ON LAST YEAR"S LIST||Halpha emission stars and Herbig-Haro objects in and around BRC||'''Luisa adds:''' YES this is useful - finding YSOs via Halpha Part of Luisa's Notes from last year: Most recent of the Sugitani series of four. Using Halpha to look for YSOs, following up their other work. relevant issues: using multiple wavelengths to find YSOs (see Finding cluster members), spatial resolution (see Resolution), caveats with finding candidates. Nice intro, summary of larger issues, discussion of results. ||http://iopscience.iop.org/1538-3881/123/5/2597/pdf/201506.web.pdf
|-
| 11. Beltran et al. 2002||IRAS 21391+5802: The Molecular Outflow and its Exciting source||'''Luisa adds:''' this is probably worth looking at to see if there is anything point source-y in here. VLA and BIMA observations of dust and gas surrounding IRAS source; 3 sources isolated with BIMA, each a YSO||http://arxiv.org/pdf/astro-ph/0203206v1.pdf
|-
| Codella et al. 2001||Star formation in the BRC of IC 1396N||'''Luisa adds:''' radio. ignore for now. The density of several different molecular outflows (dense areas of particular molecules)in the globule looked at with 30m IRAM and OVRO interferometer. Demonstrates this area very complex. ||[http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2001A%26A...376..271CFUL Astron. Astrophys., 376, 271-287 (2001)]
|-
| 12. Nisini et al. 2001||Multiple H2 protostellar jets in the bright-rimmed globule IC 1396-N||'''Luisa adds:''' jets can be HH objects, or can create them. probably useful to scan this in conjunction with some of the other outflow/hh object papers on this list. 1st detection of H2 jets from YSO. Are these HH objects? ||[http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2001A%26A...376..553N&db_key=AST&nosetcookie=1 A&A 376, 553{560]
|-
| 13. Slysh et al. 1999||Prootoplanetary disk and/or bipolar outflow traced by h2o masers in ic 1396n||'''Luisa adds:''' theoretical papers you can probably ignore. did not look at background discussion, but don't let me stop you if you are motivated! Description of 3 models that may explain how masers form; Gives background on IC 1396||http://iopscience.iop.org/0004-637X/526/1/236/pdf/39770.web.pdf
|-
| Ogura & Sugitani 1999||A large number of Halpha Emission Stars associated with BRCs||'''Luisa adds:''' conference proceedings, old at that. i'm sure this analysis is already written up in their later papers. ignore this one. Supports \"small-scale sequential star formation\"; suggests low-mass stars formating in area of high-mass star forming area||[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1999sf99.proc..381O&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf Proceedings of Star Formation, 1999, pg 381-382]
|-
| Sugitani et al. 1999||Small-Scale Sequential Star Formtion in Bright-Rimmed Clouds||'''Luisa adds:''' conference proceedings, old at that. i'm sure this analysis is already written up in their later papers. ignore this one. Discussion of small-scale sequential star formation hypothesis||[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1999sf99.proc..358S&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf Proceedings of Star Formation, 1999, pg 358-364]
|-
| 14. Saraceno et al. 1996||LWS observations of the bright-rimmed globule IC 1396N||'''Luisa adds:''' LWS is defintiely from ISO, which was a European ir mission prior to spitzer. spectrum of co, oh, h2o are detected in the ISO-LWS spectrum - not sure what that is??||[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1996A%26A...315L.293S&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf Astron. Astrophys. 315, L293–L296 (1996)]
|-
| Saraceno et al. 1996|| An evolutionary diagram for young stellar objects||'''Luisa adds:''' deep, DEEP background, IGNORE THIS. background - but not sure I understand it||[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1996A%26A...309..827S&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf Astron. Astrophys, 309, 827-839]
|-
| 15. Weikard et al. 1996||the structure of the IC 1396 region||'''Luisa adds:''' seems like this would be useful. Discussion of structure of 1c 1396 and the central star O6.5 (HD 206267) radiation on clumping and structure/location of yso; shows locations of yso in brc 38 from their data||[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1996A%26A...309..581W&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf Astron. Astrophys, 309, 581-611]
|-
| Sugitani et al. 1991 ON LAST YEAR"S LIST||A catalog of BRC with iras point sources||'''Luisa adds:''' discovery paper of BRCs, but no source lists of individual YSOs in the region. you guys should've read this already, but not relevant to the assembly of previously known YSOs in the region. Just a list of point sources they invesigated - brc 38 on the list Part of Luisa's old notes: the original SFO, origin of "BRC" terminology, numbers 1-44. covers the northern hemisphere. has nice intro/summary of what's going on in BRCs, CGs, etc. Nice approach of combining two large surveys -- POSS and IRAS; nice clear discussion of weed-down process. ||[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1991ApJS...77...59S&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf 1991, ApJS, 77, 59]
|-
| Sugitani et al. 1989||Star formation in bright-rimmed globules: evidence for radiation-driven implosion||'''Luisa adds:''' this sets up their subsequent work. you can safely ignore this. Argument for rdiation-driven implosion method of star formation.||[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1989ApJ...342L..87S&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf 1989, ApJ, 342:L87-90]
|-
| Pottasch et al. 1956||a study of bright rims in diffuse nebulae||'''Luisa adds:''' so old that not really useful for assembling list of YSOs in region. skip. Early work describing the location, shape of, density of, brightness of bright rim clouds in several nebula, including IC 1396 and Brc 38||[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1956BAN....13...77P&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf Bulletin of Astro. Instit. of the Netherlands, Vol 13, 471, 77-88]
|-
|
|}

File:Nagano 2012.pdf

2012-02-27T14:34:36Z

Bonadurer: Nagano et al (2012) paper on the Wide-Field of Emission-line Stars in IC 1396

Nagano et al (2012) paper on the Wide-Field of Emission-line Stars in IC 1396

Bob BRC 34

2012-02-23T21:50:47Z

Bonadurer: /* BRC 34 FINDINGS */

==Location of BRC 34==
As a Planetarium teacher, I wanted to know where BRC 34 was located in the sky. What constellation it was in? (Cepheus the King) What was the nearest bright star? (Alderamin & Deneb)

The image below was created using Starry Night software and Paint.

[[File:Elephant_Trunk_Nebula_Location S.JPG]]

Below is a picture of the locations of BRC 34 & 38 in IC 1396--the Elephant Trunk Nebula. I am not 100 percent sure if I got the positions correct. If anyone can double check that would be helpful.

It is curious to see the 38's brighter rim compared to 34's.

[[File:BRC_34_&_38_Locations S.JPG]]

==BRC 34 FINDINGS==

From last year’s NITARP team proposal we have the following information on BRC 34.

'''''Sugitani (1991)'''''

LOCATION: RA 21h 32m 51.2s DEC +58d 08m 43s

DISTANCE: 0.75 kilo parsecs or 2,400 light years

CLASSIFICATION: Type A BRC

'''''Ogura (2002)'''''

STARS: Found two Hα emission stars found in BRC 34.

'''Morgan (2004)'''

Defined the boundary layer of BRC 34. No 20-cm emission was associated with the rim of BRC 34. They used archival data from IRAS, NRAO/VLA Sky Survey
(NVSS), Digitized Sky Survey (DSS) and the mid-course Space experiment (MSX).

'''Valdettaro et al. (2005)'''

Did not detect water maser emissions indicative of YSOs at 22.2 GHz. They surmised that the negative results were due to the emission from the heated dust near the head of the BRC. This might also be indicative of low-mass star formation.

'''Morgan et al. (2008)'''

Found that BRC 34 did not include any T-Tauri stars nor any class I YSO candidates. They proposed that the lack of YSOs might be due to the protostellar core being at the early stages of evolution. They used SCUBA data and supplemented their findings with NASA/IPAC Infrared Science Archive data – IRAS at 12, 25, 60 and 100 μm and Two-Millimeter All-Sky Survey (2MASS) at JHKs bands. A search of the 2MASS catalog by Morgan (2008)

'''Morgan et al.(2009)'''

Eliminated BRC 34 as a good candidate for radiation driven implosion and suggested its evolution would not be affected by nearby OB stars. They used CO spectra and previous work to obtain this conclusion.

==FURTHER RESULTS for BRC 34==

'''Barensten (2011)'''

BRC 34 is defined as bright-rimmed cloud D. Though this study tripled the number (158) of classical T Tauri candidates in the IC 1396 region, most were found by bright-rimmed clouds A/B and E (BRC 38). According to Figure 9 in their study, no candidates were found near BRC 34.

Other results revealed that 56 per cent of the candidates below 0.5M—or low mass stars. Found strong indication that the formation of these clusters has been sequentially triggered by the massive star HD 206267.

'''Johnson 2012'''

This study from last year’s NITARP team found 8 new candidates for YSOs in BRC 34. There was one known before their study. Most of these YSOs (6) were classified in the flat class.

'''Saurin 2012'''

There is no direct mention of BRC 34 here, though it was studied. Indirectly we might conclude that BRC 34 has a lower central density, suggesting even smaller star clusters(?) based on the study’s finding that “BRC33, BRC36, BRC37, BRC38 and BRC39 have profiles with relatively high central density, suggesting small star clusters.”

'''Nagano 2012'''

Again, this paper did not find much activity in BRC 34 though it does state, “Some Hα stars appear to be associated with other small bright rimmed clouds such as Rim C and SFO 34 (Rim D).”

It adds though, “ total of 639 Hα emission-line stars were detected in an area of 4.2 deg2 and their i′-photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267, which is the main exciting star of the H ii region.”

==CONCLUSION==

The 2011 proposal concluded with “we will investigate the properties of this object (BRC 34) with Spitzer archival data, and compare the number of YSO candidates found here with our other target, BRC 27. The literature suggests that we will find fewer YSO candidates here than in BRC 27.

The latest research seems to suggest that this will be the case for our study in 2012--although does the WISE data in anyway suggest a different conclusion?

==Historical Narrative of IC 1396==

I just found this an interesting take on the region that contains BRC 34 & 38. From the website: (http://www.robgendlerastropics.com/IC1396text.html)

IC 1396 is a large HII region in the constellation Cepheus spanning 3 full degrees of winter sky, the same angular distance of 6 full moons. It formed at the southern edge of an enormous 400 light year bubble of molecular gas known as the Cepheus bubble. Amazingly the IC 1396 complex is illuminated by a single massive star, the class O6 star HD206267, a blue supergiant located in the center of the donut shaped emission cloud. HD206267 is member of the cluster, known as Trumpler 37, believed to be the core of the expansive Cepheus OB2 association. HD206267 is a trapezium type stellar system with HD206267 as the dominant ultraviolet energy source with a smaller UV contribution from three cooler companion B0 type stars. The stars of the entire trumpler 37 cluster are about 7 million years old, although HD206267 formed more recently about 4 million years ago.
A distinct feature of IC1396 is the radial arrangement of several bright rimmed globules that form a loose and slowly expanding ring around the illuminating stars. The ring of loosely arranged dark globules has a radius of about 40 light years with HD206267 at its center. The "comet-like" configuration of some of these dark structures has coined the descriptive term "cometary globule". Although several of the globules are optically conspicuous the most prominent is catalogued as IC 1396A. IC 1396A contains the well known reflection nebula vdB 142. Low and intermediate mass stars appear to be actively forming within the globules. The star formation within the globules has been induced by a process known as "radiation driven implosion" where the ultraviolet flux from a massive star like HD206267 compresses the cold molecular gas within the globules, thus triggering collapse of the cloud and subsequent formation of lower mass stars.

Attempts to trace the history of IC 1396 point to a complex interplay of equentially triggered star formation and cloud-cloud interactions. Events likely unfolded with an initial burst of star formation that occurred between 13 and 18 million years ago and gave rise to the first generation of stars which includes the existing nearby cluster NGC 7160. The more massive members from that first generation of stars went on to destroy themselves in supernovae explosions and no longer exist today. About 7 to 8 million years ago the effects of the first generation of supernova driven shock fronts and powerful stellar winds from existing stars created a huge 400 light year diameter bubble known as the Cepheus bubble. The expanding bubble compressed and flattened surrounding molecular clouds triggering a second burst of star formation which went on to form the Cepheus OB2 association some 7 million years ago. Also formed in this second generation of star formation were Trumpler 37 and its dominant star, HD206267 some 4 million years ago. Under the influence of the ionizing radiation field from the new star cluster, the HII cloud IC 1396 and its globules formed some 2 to 3 million years ago. Triggered by the expanding Cepheus bubble many well known HII regions have formed along its perimeter including IC 1396, Sh2-129, 133, 134, and 140. As IC 1396 expanded from the stellar winds of HD206267, surviving fragments of molecular clouds in the form of globules formed into an expanding ring around the central exciting star. The third and youngest generation of lower mass stars is currently forming within the dark globules of IC 1396 by the process of radiation driven implosion.

The bright yellow star just to the north of IC1396 is the supergiant mu cephei. It formed during the first generation of stars which created the Cepheus bubble. It has the distinction of being one of the most luminous stars in our galaxy, emitting 350,000 times the power of our sun.

Bob BRC 34

2012-02-23T21:49:13Z

Bonadurer: /* Location of BRC 34 */

==Location of BRC 34==
As a Planetarium teacher, I wanted to know where BRC 34 was located in the sky. What constellation it was in? (Cepheus the King) What was the nearest bright star? (Alderamin & Deneb)

The image below was created using Starry Night software and Paint.

[[File:Elephant_Trunk_Nebula_Location S.JPG]]

Below is a picture of the locations of BRC 34 & 38 in IC 1396--the Elephant Trunk Nebula. I am not 100 percent sure if I got the positions correct. If anyone can double check that would be helpful.

It is curious to see the 38's brighter rim compared to 34's.

[[File:BRC_34_&_38_Locations S.JPG]]

==BRC 34 FINDINGS==

From last year’s NITARP team proposal we have the following information on BRC 34.

'''''Sugitani (1991)'''''

LOCATION: RA 21h 32m 51.2s DEC +58d 08m 43s
Located in IC 1396 (Elephant Trunk’s Nebula)

DISTANCE: 0.75 kilo parsecs or 2,400 light years

CLASSIFICATION: Type A BRC

'''''Ogura (2002)'''''

STARS: Found two Hα emission stars found in BRC 34.

'''Morgan (2004)'''

Defined the boundary layer of BRC 34. No 20-cm emission was associated with the rim of BRC 34. They used archival data from IRAS, NRAO/VLA Sky Survey
(NVSS), Digitized Sky Survey (DSS) and the mid-course Space experiment (MSX).

'''Valdettaro et al. (2005)'''

Did not detect water maser emissions indicative of YSOs at 22.2 GHz. They surmised that the negative results were due to the emission from the heated dust near the head of the BRC. This might also be indicative of low-mass star formation.

'''Morgan et al. (2008)'''

Found that BRC 34 did not include any T-Tauri stars nor any class I YSO candidates. They proposed that the lack of YSOs might be due to the protostellar core being at the early stages of evolution. They used SCUBA data and supplemented their findings with NASA/IPAC Infrared Science Archive data – IRAS at 12, 25, 60 and 100 μm and Two-Millimeter All-Sky Survey (2MASS) at JHKs bands. A search of the 2MASS catalog by Morgan (2008)

'''Morgan et al.(2009)'''

Eliminated BRC 34 as a good candidate for radiation driven implosion and suggested its evolution would not be affected by nearby OB stars. They used CO spectra and previous work to obtain this conclusion.

==FURTHER RESULTS for BRC 34==

'''Barensten (2011)'''

BRC 34 is defined as bright-rimmed cloud D. Though this study tripled the number (158) of classical T Tauri candidates in the IC 1396 region, most were found by bright-rimmed clouds A/B and E (BRC 38). According to Figure 9 in their study, no candidates were found near BRC 34.

Other results revealed that 56 per cent of the candidates below 0.5M—or low mass stars. Found strong indication that the formation of these clusters has been sequentially triggered by the massive star HD 206267.

'''Johnson 2012'''

This study from last year’s NITARP team found 8 new candidates for YSOs in BRC 34. There was one known before their study. Most of these YSOs (6) were classified in the flat class.

'''Saurin 2012'''

There is no direct mention of BRC 34 here, though it was studied. Indirectly we might conclude that BRC 34 has a lower central density, suggesting even smaller star clusters(?) based on the study’s finding that “BRC33, BRC36, BRC37, BRC38 and BRC39 have profiles with relatively high central density, suggesting small star clusters.”

'''Nagano 2012'''

Again, this paper did not find much activity in BRC 34 though it does state, “Some Hα stars appear to be associated with other small bright rimmed clouds such as Rim C and SFO 34 (Rim D).”

It adds though, “ total of 639 Hα emission-line stars were detected in an area of 4.2 deg2 and their i′-photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267, which is the main exciting star of the H ii region.”

==CONCLUSION==

The 2011 proposal concluded with “we will investigate the properties of this object (BRC 34) with Spitzer archival data, and compare the number of YSO candidates found here with our other target, BRC 27. The literature suggests that we will find fewer YSO candidates here than in BRC 27.

The latest research seems to suggest that this will be the case for our study in 2012--although does the WISE data in anyway suggest a different conclusion?

==Historical Narrative of IC 1396==

I just found this an interesting take on the region that contains BRC 34 & 38. From the website: (http://www.robgendlerastropics.com/IC1396text.html)

IC 1396 is a large HII region in the constellation Cepheus spanning 3 full degrees of winter sky, the same angular distance of 6 full moons. It formed at the southern edge of an enormous 400 light year bubble of molecular gas known as the Cepheus bubble. Amazingly the IC 1396 complex is illuminated by a single massive star, the class O6 star HD206267, a blue supergiant located in the center of the donut shaped emission cloud. HD206267 is member of the cluster, known as Trumpler 37, believed to be the core of the expansive Cepheus OB2 association. HD206267 is a trapezium type stellar system with HD206267 as the dominant ultraviolet energy source with a smaller UV contribution from three cooler companion B0 type stars. The stars of the entire trumpler 37 cluster are about 7 million years old, although HD206267 formed more recently about 4 million years ago.
A distinct feature of IC1396 is the radial arrangement of several bright rimmed globules that form a loose and slowly expanding ring around the illuminating stars. The ring of loosely arranged dark globules has a radius of about 40 light years with HD206267 at its center. The "comet-like" configuration of some of these dark structures has coined the descriptive term "cometary globule". Although several of the globules are optically conspicuous the most prominent is catalogued as IC 1396A. IC 1396A contains the well known reflection nebula vdB 142. Low and intermediate mass stars appear to be actively forming within the globules. The star formation within the globules has been induced by a process known as "radiation driven implosion" where the ultraviolet flux from a massive star like HD206267 compresses the cold molecular gas within the globules, thus triggering collapse of the cloud and subsequent formation of lower mass stars.

Attempts to trace the history of IC 1396 point to a complex interplay of equentially triggered star formation and cloud-cloud interactions. Events likely unfolded with an initial burst of star formation that occurred between 13 and 18 million years ago and gave rise to the first generation of stars which includes the existing nearby cluster NGC 7160. The more massive members from that first generation of stars went on to destroy themselves in supernovae explosions and no longer exist today. About 7 to 8 million years ago the effects of the first generation of supernova driven shock fronts and powerful stellar winds from existing stars created a huge 400 light year diameter bubble known as the Cepheus bubble. The expanding bubble compressed and flattened surrounding molecular clouds triggering a second burst of star formation which went on to form the Cepheus OB2 association some 7 million years ago. Also formed in this second generation of star formation were Trumpler 37 and its dominant star, HD206267 some 4 million years ago. Under the influence of the ionizing radiation field from the new star cluster, the HII cloud IC 1396 and its globules formed some 2 to 3 million years ago. Triggered by the expanding Cepheus bubble many well known HII regions have formed along its perimeter including IC 1396, Sh2-129, 133, 134, and 140. As IC 1396 expanded from the stellar winds of HD206267, surviving fragments of molecular clouds in the form of globules formed into an expanding ring around the central exciting star. The third and youngest generation of lower mass stars is currently forming within the dark globules of IC 1396 by the process of radiation driven implosion.

The bright yellow star just to the north of IC1396 is the supergiant mu cephei. It formed during the first generation of stars which created the Cepheus bubble. It has the distinction of being one of the most luminous stars in our galaxy, emitting 350,000 times the power of our sun.

Bob BRC 34

2012-02-23T21:48:23Z

Bonadurer: /* Location of BRC 34 */

==Location of BRC 34==
As a Planetarium teacher, I wanted to know where BRC 34 was located in the sky. What constellation it was in? (Cepheus the King) What was the nearest bright star? (Alderamin & Deneb)

The image below was created using Starry Night software and Paint.

[[File:Elephant_Trunk_Nebula_Location S.JPG]]

Below is a picture of the locations of BRC 34 & 38 in IC 1396--the Elephant Trunk Nebula. I am not 100 percent sure if I got the positions correct. If anyone can double check that would be helpful.

It is curious to see the 38's brighter rim compared to 34's.

[[File:BRC_34_&_38_Locations S.jpg]]

==BRC 34 FINDINGS==

From last year’s NITARP team proposal we have the following information on BRC 34.

'''''Sugitani (1991)'''''

LOCATION: RA 21h 32m 51.2s DEC +58d 08m 43s
Located in IC 1396 (Elephant Trunk’s Nebula)

DISTANCE: 0.75 kilo parsecs or 2,400 light years

CLASSIFICATION: Type A BRC

'''''Ogura (2002)'''''

STARS: Found two Hα emission stars found in BRC 34.

'''Morgan (2004)'''

Defined the boundary layer of BRC 34. No 20-cm emission was associated with the rim of BRC 34. They used archival data from IRAS, NRAO/VLA Sky Survey
(NVSS), Digitized Sky Survey (DSS) and the mid-course Space experiment (MSX).

'''Valdettaro et al. (2005)'''

Did not detect water maser emissions indicative of YSOs at 22.2 GHz. They surmised that the negative results were due to the emission from the heated dust near the head of the BRC. This might also be indicative of low-mass star formation.

'''Morgan et al. (2008)'''

Found that BRC 34 did not include any T-Tauri stars nor any class I YSO candidates. They proposed that the lack of YSOs might be due to the protostellar core being at the early stages of evolution. They used SCUBA data and supplemented their findings with NASA/IPAC Infrared Science Archive data – IRAS at 12, 25, 60 and 100 μm and Two-Millimeter All-Sky Survey (2MASS) at JHKs bands. A search of the 2MASS catalog by Morgan (2008)

'''Morgan et al.(2009)'''

Eliminated BRC 34 as a good candidate for radiation driven implosion and suggested its evolution would not be affected by nearby OB stars. They used CO spectra and previous work to obtain this conclusion.

==FURTHER RESULTS for BRC 34==

'''Barensten (2011)'''

BRC 34 is defined as bright-rimmed cloud D. Though this study tripled the number (158) of classical T Tauri candidates in the IC 1396 region, most were found by bright-rimmed clouds A/B and E (BRC 38). According to Figure 9 in their study, no candidates were found near BRC 34.

Other results revealed that 56 per cent of the candidates below 0.5M—or low mass stars. Found strong indication that the formation of these clusters has been sequentially triggered by the massive star HD 206267.

'''Johnson 2012'''

This study from last year’s NITARP team found 8 new candidates for YSOs in BRC 34. There was one known before their study. Most of these YSOs (6) were classified in the flat class.

'''Saurin 2012'''

There is no direct mention of BRC 34 here, though it was studied. Indirectly we might conclude that BRC 34 has a lower central density, suggesting even smaller star clusters(?) based on the study’s finding that “BRC33, BRC36, BRC37, BRC38 and BRC39 have profiles with relatively high central density, suggesting small star clusters.”

'''Nagano 2012'''

Again, this paper did not find much activity in BRC 34 though it does state, “Some Hα stars appear to be associated with other small bright rimmed clouds such as Rim C and SFO 34 (Rim D).”

It adds though, “ total of 639 Hα emission-line stars were detected in an area of 4.2 deg2 and their i′-photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H ii region (Rim B and SFO 37, 38, 39, 41), and near HD 206267, which is the main exciting star of the H ii region.”

==CONCLUSION==

The 2011 proposal concluded with “we will investigate the properties of this object (BRC 34) with Spitzer archival data, and compare the number of YSO candidates found here with our other target, BRC 27. The literature suggests that we will find fewer YSO candidates here than in BRC 27.

The latest research seems to suggest that this will be the case for our study in 2012--although does the WISE data in anyway suggest a different conclusion?

==Historical Narrative of IC 1396==

I just found this an interesting take on the region that contains BRC 34 & 38. From the website: (http://www.robgendlerastropics.com/IC1396text.html)

IC 1396 is a large HII region in the constellation Cepheus spanning 3 full degrees of winter sky, the same angular distance of 6 full moons. It formed at the southern edge of an enormous 400 light year bubble of molecular gas known as the Cepheus bubble. Amazingly the IC 1396 complex is illuminated by a single massive star, the class O6 star HD206267, a blue supergiant located in the center of the donut shaped emission cloud. HD206267 is member of the cluster, known as Trumpler 37, believed to be the core of the expansive Cepheus OB2 association. HD206267 is a trapezium type stellar system with HD206267 as the dominant ultraviolet energy source with a smaller UV contribution from three cooler companion B0 type stars. The stars of the entire trumpler 37 cluster are about 7 million years old, although HD206267 formed more recently about 4 million years ago.
A distinct feature of IC1396 is the radial arrangement of several bright rimmed globules that form a loose and slowly expanding ring around the illuminating stars. The ring of loosely arranged dark globules has a radius of about 40 light years with HD206267 at its center. The "comet-like" configuration of some of these dark structures has coined the descriptive term "cometary globule". Although several of the globules are optically conspicuous the most prominent is catalogued as IC 1396A. IC 1396A contains the well known reflection nebula vdB 142. Low and intermediate mass stars appear to be actively forming within the globules. The star formation within the globules has been induced by a process known as "radiation driven implosion" where the ultraviolet flux from a massive star like HD206267 compresses the cold molecular gas within the globules, thus triggering collapse of the cloud and subsequent formation of lower mass stars.

Attempts to trace the history of IC 1396 point to a complex interplay of equentially triggered star formation and cloud-cloud interactions. Events likely unfolded with an initial burst of star formation that occurred between 13 and 18 million years ago and gave rise to the first generation of stars which includes the existing nearby cluster NGC 7160. The more massive members from that first generation of stars went on to destroy themselves in supernovae explosions and no longer exist today. About 7 to 8 million years ago the effects of the first generation of supernova driven shock fronts and powerful stellar winds from existing stars created a huge 400 light year diameter bubble known as the Cepheus bubble. The expanding bubble compressed and flattened surrounding molecular clouds triggering a second burst of star formation which went on to form the Cepheus OB2 association some 7 million years ago. Also formed in this second generation of star formation were Trumpler 37 and its dominant star, HD206267 some 4 million years ago. Under the influence of the ionizing radiation field from the new star cluster, the HII cloud IC 1396 and its globules formed some 2 to 3 million years ago. Triggered by the expanding Cepheus bubble many well known HII regions have formed along its perimeter including IC 1396, Sh2-129, 133, 134, and 140. As IC 1396 expanded from the stellar winds of HD206267, surviving fragments of molecular clouds in the form of globules formed into an expanding ring around the central exciting star. The third and youngest generation of lower mass stars is currently forming within the dark globules of IC 1396 by the process of radiation driven implosion.

The bright yellow star just to the north of IC1396 is the supergiant mu cephei. It formed during the first generation of stars which created the Cepheus bubble. It has the distinction of being one of the most luminous stars in our galaxy, emitting 350,000 times the power of our sun.