https://vmcoolwiki.ipac.caltech.edu/api.php?action=feedcontributions&feedformat=atom&user=ChildersCoolWiki - User contributions [en]2026-04-30T23:59:04ZUser contributionsMediaWiki 1.34.2https://vmcoolwiki.ipac.caltech.edu/index.php?title=Filters&diff=8574Filters2012-02-22T21:19:11Z<p>Childers: </p>
<hr />
<div>I found [http://www.astro.umd.edu/~ssm/ASTR620/mags.html this page] which was a helpful expansion on [[#David's_Original_E-Mail|David's email]] of Feb. 11. Note however that the [http://www.astro.umd.edu/~ssm/ASTR620/mags.html#flux table for Photon Flux] has different central wavelengths for the AB filters than David did (the data for the Johnson filters all match). --[[User:Childers|Childers]] 18:19, 19 February 2012 (PST)<br />
<br />
don't forget [[Units|this page]] which also may have some useful information for your discussion! :) --[[User:Rebull|Rebull]] 12:53, 22 February 2012 (PST)<br />
<br />
== Convert Johnson Magnitude to Janskys ==<br />
<br />
Solving the magnitude formula for the flux yields:<br />
<br />
<code><big>flux = 10^(-0.4*magnitude) * zero_point_flux ~ (0.3981)^magnitude * zero_point_flux</big></code><br />
<br />
<br />
<math>\phi = 10^{(-0.4m)} \phi_0 \approx (0.3981)^m \phi_0 </math><br />
<br />
<br />
Since the magnitude is a dimensionless quantity, the units for the flux will be identical to the units for the zero_point_flux. In the table below, use the right-most column. <br />
<br />
== Convert AB Magnitude to Janskys ==<br />
<br />
Because the AB magnitude system is defined by a fixed zero-point flux instead of a reference object, any AB magnitude can be converted to janskys with this formula:<br />
<br />
<code><big>flux = (0.3981)^magnitude * 3631 Jy</big></code><br />
<br />
<math> \phi = (0.3981)^m \times 3631 \mathrm{Jy} </math><br />
<br />
== David's Original E-Mail ==<br />
<br />
Dear Folks,<br />
<br />
As you know magnitudes are a logarithmic unit that runs backwards (i.e., brighter sources have smaller values). The magnitude scale is defined such that<br />
<br />
<code><big>magnitude = -2.5*log10(flux/zero_point_flux)</big></code><br />
<br />
<math>m=-2.5\log{\frac{\phi}{\phi_0}}</math><br />
<br />
where flux is the flux of the star and the zero_point_flux is the flux of a reference star DEFINED to have a magnitude = 0.0<br />
<br />
Magnitudes are useful handles on comparing the brightness of two or more sources within the same filter; i.e., source A has a magnitude of V=10 and source B has a magnitude of V=5 therefore source A is 100 times fainter). But in order to compare brightnesses of the SAME object at different filters or to compare other physical units (like the total luminosity), the magnitude scale needs to be converted to flux. For example, Vega is DEFINED to have a Johnson V=0 mag and a Johnson K = 0 mag; however, Vega is 5 times brighter in the optical (V) than it is in the infrared (K).<br />
<br />
And just to make things more complicated, there are actually two different kinds of magnitudes. There is the Johnson magnitude system (the one you are most familiar with). In this system, Vega is the standard where all magnitudes are compared to Vega which is DEFINED to have a magnitude = 0 in every filter. These filters typically include (and capitalization matters here) UBVRIJHK. In this system, the zero_point_flux for each filter changes, because the brightness of Vega changes with wavelength.<br />
<br />
<br />
{| border = "1" style="text-align:center;"<br />
!Filter <br />
!Central wave (microns) <br />
!Width wave (microns)<br />
!zero point flux (Jy)<br />
|-<br />
|U<br />
|0.36<br />
|0.15<br />
|1810<br />
|-<br />
|B<br />
|0.44<br />
|0.22<br />
|4260<br />
|-<br />
|V<br />
|0.55<br />
|0.16<br />
|3640<br />
|-<br />
|R<br />
|0.64<br />
|0.23<br />
|3080<br />
|-<br />
|I<br />
|0.79<br />
|0.19<br />
|2550<br />
|-<br />
|J<br />
|1.26<br />
|0.16<br />
|1600<br />
|-<br />
|H<br />
|1.60<br />
|0.23<br />
|1080<br />
|-<br />
|K<br />
|2.22<br />
|0.23<br />
|670<br />
|-<br />
|Ks<br />
|2.15<br />
|0.31<br />
|666.7<br />
|-<br />
|}<br />
(1 Jy = 1 Jansky = 10^-26 W Hz^-1 m^-2)<br />
<br />
<br />
There is another type of magnitude system called the AB magnitude system where Vega is not the standard, but rather every filter is DEFINED to have the same zero_point_flux of 3631 Jy for all filters in the AB system. The ugriz filters in the Kepler catalog are in the Sloan Digitized Sky Survey (SDSS) system which is an AB magnitude system.<br />
<br />
Central wavelengths of these filters are ...<br />
{| border = "1" style="text-align:center;"<br />
!u<br />
!g<br />
!r<br />
!i<br />
!z<br />
|-<br />
|0.355<br />
|0.469<br />
|0.617<br />
|0.748<br />
|0.893<br />
|}<br />
<br />
<br />
Finally, just to make things even more confusing, there are various versions of the filters (e.g., Johnson R vs Cousins R) that are similar but slightly different in wavelength or zero point flux or both. For our purposes, I would not worry so much about that.<br />
<br />
One more finally, in the KIC, you will see two filter D51 and GREDMAG - those are non-standard filters and finding conversions for those is difficult. You can collect them but I will need some time to think about how to use them.<br />
<br />
Also one more finally, I used the term flux. Actually, these conversions are from magnitude to FLUX DENSITY. A flux density is an amount of energy per time per area per unit wavelength or frequency (hence the per Hz in the units of Jansky) whereas a flux is an amount of energy per unit time per area over all wavelengths. The terminology is a detail that astronomers often use interchangeably - and often incorrectly.<br />
<br />
----<br />
<br />
[[BOKO_Current_Research_Activities|Back to the BOKO home page]]</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Filters&diff=8559Filters2012-02-21T17:17:03Z<p>Childers: </p>
<hr />
<div>I found [http://www.astro.umd.edu/~ssm/ASTR620/mags.html this page] which was a helpful expansion on [[#David's_Original_E-Mail|David's email]] of Feb. 11. Note however that the [http://www.astro.umd.edu/~ssm/ASTR620/mags.html#flux table for Photon Flux] has different central wavelengths for the AB filters than David did (the data for the Johnson filters all match). --[[User:Childers|Childers]] 18:19, 19 February 2012 (PST)<br />
<br />
== Convert Johnson Magnitude to Janskys ==<br />
<br />
Solving the magnitude formula for the flux yields:<br />
<br />
<code><big>flux = 10^(-0.4*magnitude) * zero_point_flux ~ (0.3981)^magnitude * zero_point_flux</big></code><br />
<br />
<br />
<math>f = 10^{(-0.4m)} f_0 \approx (0.3981)^m f_0 </math><br />
<br />
<br />
Since the magnitude is a dimensionless quantity, the units for the flux will be identical to the units for the zero_point_flux. In the table below, use the right-most column. <br />
<br />
== Convert AB Magnitude to Janskys ==<br />
<br />
Because the AB magnitude system is defined by a fixed zero-point flux instead of a reference object, any AB magnitude can be converted to janskys with this formula:<br />
<br />
<code><big>flux = (0.3981)^magnitude * 3631 Jy</big></code><br />
<br />
<math> \phi = (0.3981)^m \times 3631 \mathrm{Jy} </math><br />
<br />
== David's Original E-Mail ==<br />
<br />
Dear Folks,<br />
<br />
As you know magnitudes are a logarithmic unit that runs backwards (i.e., brighter sources have smaller values). The magnitude scale is defined such that<br />
<br />
<code><big>magnitude = -2.5*log10(flux/zero_point_flux)</big></code><br />
<br />
<math>m=-2.5\log{\frac{\phi}{\phi_0}}</math><br />
<br />
where flux is the flux of the star and the zero_point_flux is the flux of a reference star DEFINED to have a magnitude = 0.0<br />
<br />
Magnitudes are useful handles on comparing the brightness of two or more sources within the same filter; i.e., source A has a magnitude of V=10 and source B has a magnitude of V=5 therefore source A is 100 times fainter). But in order to compare brightnesses of the SAME object at different filters or to compare other physical units (like the total luminosity), the magnitude scale needs to be converted to flux. For example, Vega is DEFINED to have a Johnson V=0 mag and a Johnson K = 0 mag; however, Vega is 5 times brighter in the optical (V) than it is in the infrared (K).<br />
<br />
And just to make things more complicated, there are actually two different kinds of magnitudes. There is the Johnson magnitude system (the one you are most familiar with). In this system, Vega is the standard where all magnitudes are compared to Vega which is DEFINED to have a magnitude = 0 in every filter. These filters typically include (and capitalization matters here) UBVRIJHK. In this system, the zero_point_flux for each filter changes, because the brightness of Vega changes with wavelength.<br />
<br />
<br />
{| border = "1" style="text-align:center;"<br />
!Filter <br />
!Central wave (microns) <br />
!Width wave (microns)<br />
!zero point flux (Jy)<br />
|-<br />
|U<br />
|0.36<br />
|0.15<br />
|1810<br />
|-<br />
|B<br />
|0.44<br />
|0.22<br />
|4260<br />
|-<br />
|V<br />
|0.55<br />
|0.16<br />
|3640<br />
|-<br />
|R<br />
|0.64<br />
|0.23<br />
|3080<br />
|-<br />
|I<br />
|0.79<br />
|0.19<br />
|2550<br />
|-<br />
|J<br />
|1.26<br />
|0.16<br />
|1600<br />
|-<br />
|H<br />
|1.60<br />
|0.23<br />
|1080<br />
|-<br />
|K<br />
|2.22<br />
|0.23<br />
|670<br />
|-<br />
|Ks<br />
|2.15<br />
|0.31<br />
|666.7<br />
|-<br />
|}<br />
(1 Jy = 1 Jansky = 10^-26 W Hz^-1 m^-2)<br />
<br />
<br />
There is another type of magnitude system called the AB magnitude system where Vega is not the standard, but rather every filter is DEFINED to have the same zero_point_flux of 3631 Jy for all filters in the AB system. The ugriz filters in the Kepler catalog are in the Sloan Digitized Sky Survey (SDSS) system which is an AB magnitude system.<br />
<br />
Central wavelengths of these filters are ...<br />
{| border = "1" style="text-align:center;"<br />
!u<br />
!g<br />
!r<br />
!i<br />
!z<br />
|-<br />
|0.355<br />
|0.469<br />
|0.617<br />
|0.748<br />
|0.893<br />
|}<br />
<br />
<br />
Finally, just to make things even more confusing, there are various versions of the filters (e.g., Johnson R vs Cousins R) that are similar but slightly different in wavelength or zero point flux or both. For our purposes, I would not worry so much about that.<br />
<br />
One more finally, in the KIC, you will see two filter D51 and GREDMAG - those are non-standard filters and finding conversions for those is difficult. You can collect them but I will need some time to think about how to use them.<br />
<br />
Also one more finally, I used the term flux. Actually, these conversions are from magnitude to FLUX DENSITY. A flux density is an amount of energy per time per area per unit wavelength or frequency (hence the per Hz in the units of Jansky) whereas a flux is an amount of energy per unit time per area over all wavelengths. The terminology is a detail that astronomers often use interchangeably - and often incorrectly.<br />
<br />
'''''Disregard this, it is part of debugging LaTeX on this page'''''<br />
<br />
<math>B_{\lambda} = \left(\frac{2hc^2/\lambda^5}{\exp(hc/\lambda kT)-1)}\right)</math><br />
<br />
----<br />
<br />
[[BOKO_Current_Research_Activities|Back to the BOKO home page]]</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=SIMBAD&diff=8558SIMBAD2012-02-21T17:16:39Z<p>Childers: </p>
<hr />
<div><br />
== Downloading Magnitudes from a List of Identifiers to a Spreadsheet ==<br />
<br />
# '''Start on the [http://simbad.u-strasbg.fr/simbad/ SIMBAD home page.]''' Look on the left for <font color="red">''Queries''</font>, and then underneath that click on ''by identifier''.<br />
# '''Set Output Options'''<br />
## Click on '''Output Options''', which is in a yellow box on the right-hand side of the '''''other query modes''''' row along the top. A new browser tab will open.<br />
## Set the '''Output Format''' in the top row.<br />
### Choose '''ASCII (;-separator for spreadsheet)''' from the drop-down menu.<br />
### Check '''file output'''.<br />
## Make changes to the '''List Display''' column.<br />
### Make sure '''Identifier''' is checked.<br />
### Make sure '''Coordinates 1''' is checked, and then choose "ICRS", epoch "J2000", equinox "2000", and format "decimal". These coordinates are what GALEX will want so you may as well get them now.<br />
### Make sure '''Fluxes/Magnitudes''' is checked<br />
### You must also check the '''individual filters''' in the right-hand cells of the Fluxes/Magnitudes row. You have nothing to lose by clicking all of them.<br />
### In general, uncheck all other rows, unless you are suspicious about your target list and would like some extra columns in your spreadsheet to act as a reality check.<br />
## Click the '''SAVE''' button at the bottom to set a browser cookie and save your changes.<br />
# '''Query a List of Identifiers''' is on the bottom half of the original SIMBAD query browser tab.<br />
## Prepare a '''.txt''' Notepad file containing only SIMBAD acceptable identifiers without a header. Chances are if you got your list of identifiers from a catalog, you'll be okay. <br />
## Click '''Choose File''' and browse to your text file.<br />
## Check '''''list display'''''.<br />
## Check '''Submit File'''.<br />
# '''A .csv file will begin downloading automatically.'''<br />
::* Since semicolon is not the default delimiter in Excel, either use File > Open and then Data > Text to Columns, or use Data > Import External Data > Import Data.<br />
::* The first few rows of the file identify and timestamp the query<br />
::* Missing magnitudes for a given filter are shown with a tilde (~) symbol. Use Edit > Replace to get rid of them.<br />
::* Identifiers from the uploaded list that SIMBAD couldn't parse are listed separately at the end.<br />
<br />
--[[User:Childers|Childers]] 15:21, 19 February 2012 (PST)<br />
<br />
----<br />
<br />
[[BOKO_Current_Research_Activities|Back to the BOKO home page]]</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Galex&diff=8557Galex2012-02-21T17:16:20Z<p>Childers: </p>
<hr />
<div>When I "save as" and try to look at the file with Excel, it is a mess. Advice? Is anyone having more success?<br />
<br />
----<br />
<br />
[[BOKO_Current_Research_Activities|Back to the BOKO home page]]</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Kepler&diff=8556Kepler2012-02-21T17:16:09Z<p>Childers: </p>
<hr />
<div>When you do a search in Kepler, be sure to scroll to the bottom of the search page to edit the "Output Columns." You can get more data this way.<br />
<br />
----<br />
<br />
[[BOKO_Current_Research_Activities|Back to the BOKO home page]]</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Starting_Email_from_Ciardi_-_20_Jan_2012&diff=8552Starting Email from Ciardi - 20 Jan 20122012-02-21T17:14:55Z<p>Childers: </p>
<hr />
<div>==Notes by Ciardi on Places to start looking for photometric data.==<br />
<br />
I started by writing up a '''[http://coolwiki.ipac.caltech.edu/images/2/2a/Tutorial_20120119a.pdf tutorial]''' on how to do general searches and which websites to start with.<br />
<br />
Related to this, Steve and I have provided a list of test objects for you to practice searching on.<br />
<br />
* Steve collected for me the the blue objects that we know to be white dwarfs, cataclysmic variables, planetary nebulae, and active nuclei of galaxies. That list is given in the attached file testset.tbl<br />
<br />
* Because the various only services typically do not like files with so many comments and coordinates listed in hours/degrees, minutes, and seconds, I have compacted this file and converted the coordinates into decimal degrees (see below and attached pdf file), and I have made this file a comma separated file (csv). This means that excel will read it as well as normal text editors, but more importantly, the online services can read it. This file is testset.csv (although be warned, some services only want RA, Dec and you may need to make changes to this file to get it to work with some services - again see the pdf file).<br />
<br />
* And now the pdf file - I have tried to think about this project from the point of view of where would I start, and how would I proceed. I tried to put into a somewhat condensed tutorial. I am hoping this pdf file will help you get started - in particular, I hope you take this as a starting point to explore and play with the various sites.<br />
<br />
* What I would like to see each of you do is try to collect information and on each of the objects in the test sample so you can become familiar with the services.<br />
<br />
Objects were in two files ... first file (testset.tbl) they were grouped by category and coordinates were in sexagesimal, second file (testset.csv), coordinates converted to decimal degrees and file formated for general upload services (but not always ---)<br />
<br />
----<br />
<br />
[[BOKO_Current_Research_Activities|Back to the BOKO home page]]</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Filters&diff=8541Filters2012-02-20T17:58:46Z<p>Childers: </p>
<hr />
<div>I found [http://www.astro.umd.edu/~ssm/ASTR620/mags.html this page] which was a helpful expansion on [[#David's_Original_E-Mail|David's email]] of Feb. 11. Note however that the [http://www.astro.umd.edu/~ssm/ASTR620/mags.html#flux table for Photon Flux] has different central wavelengths for the AB filters than David did (the data for the Johnson filters all match). --[[User:Childers|Childers]] 18:19, 19 February 2012 (PST)<br />
<br />
== Convert Johnson Magnitude to Janskys ==<br />
<br />
Solving the magnitude formula for the flux yields:<br />
<br />
<code><big>flux = 10^(-0.4*magnitude) * zero_point_flux ~ (0.3981)^magnitude * zero_point_flux</big></code><br />
<br />
<math> \phi = 10 ^{(-0.4m)} \phi_0 \approx (0.3981)^m \phi_0 </math><br />
<br />
Since the magnitude is a dimensionless quantity, the units for the flux will be identical to the units for the zero_point_flux. In the table below, use the right-most column. <br />
<br />
== Convert AB Magnitude to Janskys ==<br />
<br />
Because the AB magnitude system is defined by a fixed zero-point flux instead of a reference object, any AB magnitude can be converted to janskys with this formula:<br />
<br />
<code><big>flux = (0.3981)^magnitude * 3631 Jy</big></code><br />
<br />
<math> \phi = (0.3981)^m \times 3631 \mathrm{Jy} </math><br />
<br />
== David's Original E-Mail ==<br />
<br />
Dear Folks,<br />
<br />
As you know magnitudes are a logarithmic unit that runs backwards (i.e., brighter sources have smaller values). The magnitude scale is defined such that<br />
<br />
<code><big>magnitude = -2.5*log10(flux/zero_point_flux)</big></code><br />
<br />
<math>m=-2.5\log{\frac{\phi}{\phi_0}}</math><br />
<br />
where flux is the flux of the star and the zero_point_flux is the flux of a reference star DEFINED to have a magnitude = 0.0<br />
<br />
Magnitudes are useful handles on comparing the brightness of two or more sources within the same filter; i.e., source A has a magnitude of V=10 and source B has a magnitude of V=5 therefore source A is 100 times fainter). But in order to compare brightnesses of the SAME object at different filters or to compare other physical units (like the total luminosity), the magnitude scale needs to be converted to flux. For example, Vega is DEFINED to have a Johnson V=0 mag and a Johnson K = 0 mag; however, Vega is 5 times brighter in the optical (V) than it is in the infrared (K).<br />
<br />
And just to make things more complicated, there are actually two different kinds of magnitudes. There is the Johnson magnitude system (the one you are most familiar with). In this system, Vega is the standard where all magnitudes are compared to Vega which is DEFINED to have a magnitude = 0 in every filter. These filters typically include (and capitalization matters here) UBVRIJHK. In this system, the zero_point_flux for each filter changes, because the brightness of Vega changes with wavelength.<br />
<br />
<br />
{| border = "1" style="text-align:center;"<br />
!Filter <br />
!Central wave (microns) <br />
!Width wave (microns)<br />
!zero point flux (Jy)<br />
|-<br />
|U<br />
|0.36<br />
|0.15<br />
|1810<br />
|-<br />
|B<br />
|0.44<br />
|0.22<br />
|4260<br />
|-<br />
|V<br />
|0.55<br />
|0.16<br />
|3640<br />
|-<br />
|R<br />
|0.64<br />
|0.23<br />
|3080<br />
|-<br />
|I<br />
|0.79<br />
|0.19<br />
|2550<br />
|-<br />
|J<br />
|1.26<br />
|0.16<br />
|1600<br />
|-<br />
|H<br />
|1.60<br />
|0.23<br />
|1080<br />
|-<br />
|K<br />
|2.22<br />
|0.23<br />
|670<br />
|-<br />
|Ks<br />
|2.15<br />
|0.31<br />
|666.7<br />
|-<br />
|}<br />
(1 Jy = 1 Jansky = 10^-26 W Hz^-1 m^-2)<br />
<br />
<br />
There is another type of magnitude system called the AB magnitude system where Vega is not the standard, but rather every filter is DEFINED to have the same zero_point_flux of 3631 Jy for all filters in the AB system. The ugriz filters in the Kepler catalog are in the Sloan Digitized Sky Survey (SDSS) system which is an AB magnitude system.<br />
<br />
Central wavelengths of these filters are ...<br />
{| border = "1" style="text-align:center;"<br />
!u<br />
!g<br />
!r<br />
!i<br />
!z<br />
|-<br />
|0.355<br />
|0.469<br />
|0.617<br />
|0.748<br />
|0.893<br />
|}<br />
<br />
<br />
Finally, just to make things even more confusing, there are various versions of the filters (e.g., Johnson R vs Cousins R) that are similar but slightly different in wavelength or zero point flux or both. For our purposes, I would not worry so much about that.<br />
<br />
One more finally, in the KIC, you will see two filter D51 and GREDMAG - those are non-standard filters and finding conversions for those is difficult. You can collect them but I will need some time to think about how to use them.<br />
<br />
Also one more finally, I used the term flux. Actually, these conversions are from magnitude to FLUX DENSITY. A flux density is an amount of energy per time per area per unit wavelength or frequency (hence the per Hz in the units of Jansky) whereas a flux is an amount of energy per unit time per area over all wavelengths. The terminology is a detail that astronomers often use interchangeably - and often incorrectly.<br />
<br />
'''''Disregard this, it is part of debugging LaTex on this page'''''<br />
<br />
<math>B_{\lambda} = \left(\frac{2hc^2/\lambda^5}{\exp(hc/\lambda kT)-1)}\right)</math></div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Filters&diff=8538Filters2012-02-20T17:45:07Z<p>Childers: </p>
<hr />
<div>I found [http://www.astro.umd.edu/~ssm/ASTR620/mags.html this page] which was a helpful expansion on [[#David's_Original_E-Mail|David's email]] of Feb. 11. Note however that the [http://www.astro.umd.edu/~ssm/ASTR620/mags.html#flux table for Photon Flux] has different central wavelengths for the AB filters than David did (the data for the Johnson filters all match). --[[User:Childers|Childers]] 18:19, 19 February 2012 (PST)<br />
<br />
== Convert Johnson Magnitude to Janskys ==<br />
<br />
Solving the magnitude formula for the flux yields:<br />
<br />
<code><big>flux = 10^(-0.4*magnitude) * zero_point_flux ~ (0.3981)^magnitude * zero_point_flux</big></code><br />
<br />
<math> \phi = 10 ^{(-0.4m)} \phi_0 \approx (0.3981)^m \phi_0 </math><br />
<br />
Since the magnitude is a dimensionless quantity, the units for the flux will be identical to the units for the zero_point_flux. In the table below, use the right-most column. <br />
<br />
== Convert AB Magnitude to Janskys ==<br />
<br />
Because the AB magnitude system is defined by a fixed zero-point flux instead of a reference object, any AB magnitude can be converted to janskys with this formula:<br />
<br />
<code><big>flux = (0.3981)^magnitude * 3631 Jy</big></code><br />
<br />
<math> \phi = (0.3981)^m \times 3631 \mathrm{Jy} </math><br />
<br />
== David's Original E-Mail ==<br />
<br />
Dear Folks,<br />
<br />
As you know magnitudes are a logarithmic unit that runs backwards (i.e., brighter sources have smaller values). The magnitude scale is defined such that<br />
<br />
<code><big>magnitude = -2.5*log10(flux/zero_point_flux)</big></code><br />
<br />
<math> m = -2.5 \log{\frac{\phi}{\phi_0}} </math><br />
<br />
where flux is the flux of the star and the zero_point_flux is the flux of a reference star DEFINED to have a magnitude = 0.0<br />
<br />
Magnitudes are useful handles on comparing the brightness of two or more sources within the same filter; i.e., source A has a magnitude of V=10 and source B has a magnitude of V=5 therefore source A is 100 times fainter). But in order to compare brightnesses of the SAME object at different filters or to compare other physical units (like the total luminosity), the magnitude scale needs to be converted to flux. For example, Vega is DEFINED to have a Johnson V=0 mag and a Johnson K = 0 mag; however, Vega is 5 times brighter in the optical (V) than it is in the infrared (K).<br />
<br />
And just to make things more complicated, there are actually two different kinds of magnitudes. There is the Johnson magnitude system (the one you are most familiar with). In this system, Vega is the standard where all magnitudes are compared to Vega which is DEFINED to have a magnitude = 0 in every filter. These filters typically include (and capitalization matters here) UBVRIJHK. In this system, the zero_point_flux for each filter changes, because the brightness of Vega changes with wavelength.<br />
<br />
<br />
{| border = "1" style="text-align:center;"<br />
!Filter <br />
!Central wave (microns) <br />
!Width wave (microns)<br />
!zero point flux (Jy)<br />
|-<br />
|U<br />
|0.36<br />
|0.15<br />
|1810<br />
|-<br />
|B<br />
|0.44<br />
|0.22<br />
|4260<br />
|-<br />
|V<br />
|0.55<br />
|0.16<br />
|3640<br />
|-<br />
|R<br />
|0.64<br />
|0.23<br />
|3080<br />
|-<br />
|I<br />
|0.79<br />
|0.19<br />
|2550<br />
|-<br />
|J<br />
|1.26<br />
|0.16<br />
|1600<br />
|-<br />
|H<br />
|1.60<br />
|0.23<br />
|1080<br />
|-<br />
|K<br />
|2.22<br />
|0.23<br />
|670<br />
|-<br />
|Ks<br />
|2.15<br />
|0.31<br />
|666.7<br />
|-<br />
|}<br />
(1 Jy = 1 Jansky = 10^-26 W Hz^-1 m^-2)<br />
<br />
<br />
There is another type of magnitude system called the AB magnitude system where Vega is not the standard, but rather every filter is DEFINED to have the same zero_point_flux of 3631 Jy for all filters in the AB system. The ugriz filters in the Kepler catalog are in the Sloan Digitized Sky Survey (SDSS) system which is an AB magnitude system.<br />
<br />
Central wavelengths of these filters are ...<br />
{| border = "1" style="text-align:center;"<br />
!u<br />
!g<br />
!r<br />
!i<br />
!z<br />
|-<br />
|0.355<br />
|0.469<br />
|0.617<br />
|0.748<br />
|0.893<br />
|}<br />
<br />
<br />
Finally, just to make things even more confusing, there are various versions of the filters (e.g., Johnson R vs Cousins R) that are similar but slightly different in wavelength or zero point flux or both. For our purposes, I would not worry so much about that.<br />
<br />
One more finally, in the KIC, you will see two filter D51 and GREDMAG - those are non-standard filters and finding conversions for those is difficult. You can collect them but I will need some time to think about how to use them.<br />
<br />
Also one more finally, I used the term flux. Actually, these conversions are from magnitude to FLUX DENSITY. A flux density is an amount of energy per time per area per unit wavelength or frequency (hence the per Hz in the units of Jansky) whereas a flux is an amount of energy per unit time per area over all wavelengths. The terminology is a detail that astronomers often use interchangeably - and often incorrectly.</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=SIMBAD&diff=8537SIMBAD2012-02-20T13:40:14Z<p>Childers: </p>
<hr />
<div><br />
== Downloading Magnitudes from a List of Identifiers to a Spreadsheet ==<br />
<br />
# '''Start on the [http://simbad.u-strasbg.fr/simbad/ SIMBAD home page.]''' Look on the left for <font color="red">''Queries''</font>, and then underneath that click on ''by identifier''.<br />
# '''Set Output Options'''<br />
## Click on '''Output Options''', which is in a yellow box on the right-hand side of the '''''other query modes''''' row along the top. A new browser tab will open.<br />
## Set the '''Output Format''' in the top row.<br />
### Choose '''ASCII (;-separator for spreadsheet)''' from the drop-down menu.<br />
### Check '''file output'''.<br />
## Make changes to the '''List Display''' column.<br />
### Make sure '''Identifier''' is checked.<br />
### Make sure '''Coordinates 1''' is checked, and then choose "ICRS", epoch "J2000", equinox "2000", and format "decimal". These coordinates are what GALEX will want so you may as well get them now.<br />
### Make sure '''Fluxes/Magnitudes''' is checked<br />
### You must also check the '''individual filters''' in the right-hand cells of the Fluxes/Magnitudes row. You have nothing to lose by clicking all of them.<br />
### In general, uncheck all other rows, unless you are suspicious about your target list and would like some extra columns in your spreadsheet to act as a reality check.<br />
## Click the '''SAVE''' button at the bottom to set a browser cookie and save your changes.<br />
# '''Query a List of Identifiers''' is on the bottom half of the original SIMBAD query browser tab.<br />
## Prepare a '''.txt''' Notepad file containing only SIMBAD acceptable identifiers without a header. Chances are if you got your list of identifiers from a catalog, you'll be okay. <br />
## Click '''Choose File''' and browse to your text file.<br />
## Check '''''list display'''''.<br />
## Check '''Submit File'''.<br />
# '''A .csv file will begin downloading automatically.'''<br />
::* Since semicolon is not the default delimiter in Excel, either use File > Open and then Data > Text to Columns, or use Data > Import External Data > Import Data.<br />
::* The first few rows of the file identify and timestamp the query<br />
::* Missing magnitudes for a given filter are shown with a tilde (~) symbol. Use Edit > Replace to get rid of them.<br />
::* Identifiers from the uploaded list that SIMBAD couldn't parse are listed separately at the end.<br />
<br />
--[[User:Childers|Childers]] 15:21, 19 February 2012 (PST)</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Filters&diff=8536Filters2012-02-20T13:28:42Z<p>Childers: </p>
<hr />
<div>I found [http://www.astro.umd.edu/~ssm/ASTR620/mags.html this page] which was a helpful expansion on [[#David's_Original_E-Mail|David's email]] of Feb. 11. Note however that the [http://www.astro.umd.edu/~ssm/ASTR620/mags.html#flux table for Photon Flux] has different central wavelengths for the AB filters than David did (the data for the Johnson filters all match). --[[User:Childers|Childers]] 18:19, 19 February 2012 (PST)<br />
<br />
== Convert Johnson Magnitude to Janskys ==<br />
<br />
Solving the magnitude formula for the flux yields:<br />
<br />
<code><big>flux = 10^(-0.4*magnitude) * zero_point_flux ~ (0.3981)^magnitude * zero_point_flux</big></code><br />
<br />
Since the magnitude is a dimensionless quantity, the units for the flux will be identical to the units for the zero_point_flux. In the table below, use the right-most column. <br />
<br />
== Convert AB Magnitude to Janskys ==<br />
<br />
Because the AB magnitude system is defined by a fixed zero-point flux instead of a reference object, any AB magnitude can be converted to janskys with this formula:<br />
<br />
<code><big>flux = (0.3981)^magnitude * 3631 Jy</big></code><br />
<br />
== David's Original E-Mail ==<br />
<br />
Dear Folks,<br />
<br />
As you know magnitudes are a logarithmic unit that runs backwards (i.e., brighter sources have smaller values). The magnitude scale is defined such that<br />
<br />
<code><big>magnitude = -2.5*log10(flux/zero_point_flux)</big></code><br />
<br />
where flux is the flux of the star and the zero_point_flux is the flux of a reference star DEFINED to have a magnitude = 0.0<br />
<br />
Magnitudes are useful handles on comparing the brightness of two or more sources within the same filter; i.e., source A has a magnitude of V=10 and source B has a magnitude of V=5 therefore source A is 100 times fainter). But in order to compare brightnesses of the SAME object at different filters or to compare other physical units (like the total luminosity), the magnitude scale needs to be converted to flux. For example, Vega is DEFINED to have a Johnson V=0 mag and a Johnson K = 0 mag; however, Vega is 5 times brighter in the optical (V) than it is in the infrared (K).<br />
<br />
And just to make things more complicated, there are actually two different kinds of magnitudes. There is the Johnson magnitude system (the one you are most familiar with). In this system, Vega is the standard where all magnitudes are compared to Vega which is DEFINED to have a magnitude = 0 in every filter. These filters typically include (and capitalization matters here) UBVRIJHK. In this system, the zero_point_flux for each filter changes, because the brightness of Vega changes with wavelength.<br />
<br />
<br />
{| border = "1" style="text-align:center;"<br />
!Filter <br />
!Central wave (microns) <br />
!Width wave (microns)<br />
!zero point flux (Jy)<br />
|-<br />
|U<br />
|0.36<br />
|0.15<br />
|1810<br />
|-<br />
|B<br />
|0.44<br />
|0.22<br />
|4260<br />
|-<br />
|V<br />
|0.55<br />
|0.16<br />
|3640<br />
|-<br />
|R<br />
|0.64<br />
|0.23<br />
|3080<br />
|-<br />
|I<br />
|0.79<br />
|0.19<br />
|2550<br />
|-<br />
|J<br />
|1.26<br />
|0.16<br />
|1600<br />
|-<br />
|H<br />
|1.60<br />
|0.23<br />
|1080<br />
|-<br />
|K<br />
|2.22<br />
|0.23<br />
|670<br />
|-<br />
|Ks<br />
|2.15<br />
|0.31<br />
|666.7<br />
|-<br />
|}<br />
(1 Jy = 1 Jansky = 10^-26 W Hz^-1 m^-2)<br />
<br />
<br />
There is another type of magnitude system called the AB magnitude system where Vega is not the standard, but rather every filter is DEFINED to have the same zero_point_flux of 3631 Jy for all filters in the AB system. The ugriz filters in the Kepler catalog are in the Sloan Digitized Sky Survey (SDSS) system which is an AB magnitude system.<br />
<br />
Central wavelengths of these filters are ...<br />
{| border = "1" style="text-align:center;"<br />
!u<br />
!g<br />
!r<br />
!i<br />
!z<br />
|-<br />
|0.355<br />
|0.469<br />
|0.617<br />
|0.748<br />
|0.893<br />
|}<br />
<br />
<br />
Finally, just to make things even more confusing, there are various versions of the filters (e.g., Johnson R vs Cousins R) that are similar but slightly different in wavelength or zero point flux or both. For our purposes, I would not worry so much about that.<br />
<br />
One more finally, in the KIC, you will see two filter D51 and GREDMAG - those are non-standard filters and finding conversions for those is difficult. You can collect them but I will need some time to think about how to use them.<br />
<br />
Also one more finally, I used the term flux. Actually, these conversions are from magnitude to FLUX DENSITY. A flux density is an amount of energy per time per area per unit wavelength or frequency (hence the per Hz in the units of Jansky) whereas a flux is an amount of energy per unit time per area over all wavelengths. The terminology is a detail that astronomers often use interchangeably - and often incorrectly.</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Filters&diff=8535Filters2012-02-20T02:19:07Z<p>Childers: </p>
<hr />
<div>I found [http://www.astro.umd.edu/~ssm/ASTR620/mags.html this page] which was a helpful expansion on [[#David's_Original_E-Mail|David's email]] of Feb. 11. Note however that the [http://www.astro.umd.edu/~ssm/ASTR620/mags.html#flux table for Photon Flux] has different central wavelengths for the AB filters than David did (the data for the Johnson filters all match). --[[User:Childers|Childers]] 18:19, 19 February 2012 (PST)<br />
<br />
<!-- == Convert Johnson Magnitude to Janksy == --><br />
== David's Original E-Mail ==<br />
<br />
Dear Folks,<br />
<br />
As you know magnitudes are a logarithmic unit that runs backwards (i.e., brighter sources have smaller values). The magnitude scale is defined such that<br />
<br />
<code><big>magnitude = -2.5*log10(flux/zero_point_flux)</big></code><br />
<br />
where flux is the flux of the star and the zero_point_flux is the flux of a reference star DEFINED to have a magnitude = 0.0<br />
<br />
Magnitudes are useful handles on comparing the brightness of two or more sources within the same filter; i.e., source A has a magnitude of V=10 and source B has a magnitude of V=5 therefore source A is 100 times fainter). But in order to compare brightnesses of the SAME object at different filters or to compare other physical units (like the total luminosity), the magnitude scale needs to be converted to flux. For example, Vega is DEFINED to have a Johnson V=0 mag and a Johnson K = 0 mag; however, Vega is 5 times brighter in the optical (V) than it is in the infrared (K).<br />
<br />
And just to make things more complicated, there are actually two different kinds of magnitudes. There is the Johnson magnitude system (the one you are most familiar with). In this system, Vega is the standard where all magnitudes are compared to Vega which is DEFINED to have a magnitude = 0 in every filter. These filters typically include (and capitalization matters here) UBVRIJHK. In this system, the zero_point_flux for each filter changes, because the brightness of Vega changes with wavelength.<br />
<br />
<br />
{| border = "1" style="text-align:center;"<br />
!Filter <br />
!Central wave (microns) <br />
!Width wave (microns)<br />
!zero point flux (Jy)<br />
|-<br />
|U<br />
|0.36<br />
|0.15<br />
|1810<br />
|-<br />
|B<br />
|0.44<br />
|0.22<br />
|4260<br />
|-<br />
|V<br />
|0.55<br />
|0.16<br />
|3640<br />
|-<br />
|R<br />
|0.64<br />
|0.23<br />
|3080<br />
|-<br />
|I<br />
|0.79<br />
|0.19<br />
|2550<br />
|-<br />
|J<br />
|1.26<br />
|0.16<br />
|1600<br />
|-<br />
|H<br />
|1.60<br />
|0.23<br />
|1080<br />
|-<br />
|K<br />
|2.22<br />
|0.23<br />
|670<br />
|-<br />
|Ks<br />
|2.15<br />
|0.31<br />
|666.7<br />
|-<br />
|}<br />
(1 Jy = 1 Jansky = 10^-26 W Hz^-1 m^-2)<br />
<br />
<br />
There is another type of magnitude system called the AB magnitude system where Vega is not the standard, but rather every filter is DEFINED to have the same zero_point_flux of 3631 Jy for all filters in the AB system. The ugriz filters in the Kepler catalog are in the Sloan Digitized Sky Survey (SDSS) system which is an AB magnitude system.<br />
<br />
Central wavelengths of these filters are ...<br />
{| border = "1" style="text-align:center;"<br />
!u<br />
!g<br />
!r<br />
!i<br />
!z<br />
|-<br />
|0.355<br />
|0.469<br />
|0.617<br />
|0.748<br />
|0.893<br />
|}<br />
<br />
<br />
Finally, just to make things even more confusing, there are various versions of the filters (e.g., Johnson R vs Cousins R) that are similar but slightly different in wavelength or zero point flux or both. For our purposes, I would not worry so much about that.<br />
<br />
One more finally, in the KIC, you will see two filter D51 and GREDMAG - those are non-standard filters and finding conversions for those is difficult. You can collect them but I will need some time to think about how to use them.<br />
<br />
Also one more finally, I used the term flux. Actually, these conversions are from magnitude to FLUX DENSITY. A flux density is an amount of energy per time per area per unit wavelength or frequency (hence the per Hz in the units of Jansky) whereas a flux is an amount of energy per unit time per area over all wavelengths. The terminology is a detail that astronomers often use interchangeably - and often incorrectly.</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Filters&diff=8534Filters2012-02-20T02:18:19Z<p>Childers: </p>
<hr />
<div>I found [http://www.astro.umd.edu/~ssm/ASTR620/mags.html this page] which was a helpful expansion on [[#David's_Original_E-Mail|David's email]] of Feb. 11. Note however that the [http://www.astro.umd.edu/~ssm/ASTR620/mags.html#flux table for Photon Flux] has different central wavelengths for the AB filters than David did (the data for the Johnson filters all match).<br />
<br />
<!-- == Convert Johnson Magnitude to Janksy == --><br />
== David's Original E-Mail ==<br />
<br />
Dear Folks,<br />
<br />
As you know magnitudes are a logarithmic unit that runs backwards (i.e., brighter sources have smaller values). The magnitude scale is defined such that<br />
<br />
<code><big>magnitude = -2.5*log10(flux/zero_point_flux)</big></code><br />
<br />
where flux is the flux of the star and the zero_point_flux is the flux of a reference star DEFINED to have a magnitude = 0.0<br />
<br />
Magnitudes are useful handles on comparing the brightness of two or more sources within the same filter; i.e., source A has a magnitude of V=10 and source B has a magnitude of V=5 therefore source A is 100 times fainter). But in order to compare brightnesses of the SAME object at different filters or to compare other physical units (like the total luminosity), the magnitude scale needs to be converted to flux. For example, Vega is DEFINED to have a Johnson V=0 mag and a Johnson K = 0 mag; however, Vega is 5 times brighter in the optical (V) than it is in the infrared (K).<br />
<br />
And just to make things more complicated, there are actually two different kinds of magnitudes. There is the Johnson magnitude system (the one you are most familiar with). In this system, Vega is the standard where all magnitudes are compared to Vega which is DEFINED to have a magnitude = 0 in every filter. These filters typically include (and capitalization matters here) UBVRIJHK. In this system, the zero_point_flux for each filter changes, because the brightness of Vega changes with wavelength.<br />
<br />
<br />
{| border = "1" style="text-align:center;"<br />
!Filter <br />
!Central wave (microns) <br />
!Width wave (microns)<br />
!zero point flux (Jy)<br />
|-<br />
|U<br />
|0.36<br />
|0.15<br />
|1810<br />
|-<br />
|B<br />
|0.44<br />
|0.22<br />
|4260<br />
|-<br />
|V<br />
|0.55<br />
|0.16<br />
|3640<br />
|-<br />
|R<br />
|0.64<br />
|0.23<br />
|3080<br />
|-<br />
|I<br />
|0.79<br />
|0.19<br />
|2550<br />
|-<br />
|J<br />
|1.26<br />
|0.16<br />
|1600<br />
|-<br />
|H<br />
|1.60<br />
|0.23<br />
|1080<br />
|-<br />
|K<br />
|2.22<br />
|0.23<br />
|670<br />
|-<br />
|Ks<br />
|2.15<br />
|0.31<br />
|666.7<br />
|-<br />
|}<br />
(1 Jy = 1 Jansky = 10^-26 W Hz^-1 m^-2)<br />
<br />
<br />
There is another type of magnitude system called the AB magnitude system where Vega is not the standard, but rather every filter is DEFINED to have the same zero_point_flux of 3631 Jy for all filters in the AB system. The ugriz filters in the Kepler catalog are in the Sloan Digitized Sky Survey (SDSS) system which is an AB magnitude system.<br />
<br />
Central wavelengths of these filters are ...<br />
{| border = "1" style="text-align:center;"<br />
!u<br />
!g<br />
!r<br />
!i<br />
!z<br />
|-<br />
|0.355<br />
|0.469<br />
|0.617<br />
|0.748<br />
|0.893<br />
|}<br />
<br />
<br />
Finally, just to make things even more confusing, there are various versions of the filters (e.g., Johnson R vs Cousins R) that are similar but slightly different in wavelength or zero point flux or both. For our purposes, I would not worry so much about that.<br />
<br />
One more finally, in the KIC, you will see two filter D51 and GREDMAG - those are non-standard filters and finding conversions for those is difficult. You can collect them but I will need some time to think about how to use them.<br />
<br />
Also one more finally, I used the term flux. Actually, these conversions are from magnitude to FLUX DENSITY. A flux density is an amount of energy per time per area per unit wavelength or frequency (hence the per Hz in the units of Jansky) whereas a flux is an amount of energy per unit time per area over all wavelengths. The terminology is a detail that astronomers often use interchangeably - and often incorrectly.</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Filters&diff=8533Filters2012-02-20T02:16:00Z<p>Childers: </p>
<hr />
<div>I found [http://www.astro.umd.edu/~ssm/ASTR620/mags.html this page] which was a helpful expansion on David's email of Feb. 11. Note however that the [http://www.astro.umd.edu/~ssm/ASTR620/mags.html#flux table for Photon Flux] has different central wavelengths for the AB filters than David did (the data for the Johnson filters all match).<br />
<br />
<!-- == Convert Johnson Magnitude to Janksy == --><br />
== David's Original E-Mail ==<br />
<br />
Dear Folks,<br />
<br />
As you know magnitudes are a logarithmic unit that runs backwards (i.e., brighter sources have smaller values). The magnitude scale is defined such that<br />
<br />
<code><big>magnitude = -2.5*log10(flux/zero_point_flux)</big></code><br />
<br />
where flux is the flux of the star and the zero_point_flux is the flux of a reference star DEFINED to have a magnitude = 0.0<br />
<br />
Magnitudes are useful handles on comparing the brightness of two or more sources within the same filter; i.e., source A has a magnitude of V=10 and source B has a magnitude of V=5 therefore source A is 100 times fainter). But in order to compare brightnesses of the SAME object at different filters or to compare other physical units (like the total luminosity), the magnitude scale needs to be converted to flux. For example, Vega is DEFINED to have a Johnson V=0 mag and a Johnson K = 0 mag; however, Vega is 5 times brighter in the optical (V) than it is in the infrared (K).<br />
<br />
And just to make things more complicated, there are actually two different kinds of magnitudes. There is the Johnson magnitude system (the one you are most familiar with). In this system, Vega is the standard where all magnitudes are compared to Vega which is DEFINED to have a magnitude = 0 in every filter. These filters typically include (and capitalization matters here) UBVRIJHK. In this system, the zero_point_flux for each filter changes, because the brightness of Vega changes with wavelength.<br />
<br />
<br />
{| border = "1" style="text-align:center;"<br />
!Filter <br />
!Central wave (microns) <br />
!Width wave (microns)<br />
!zero point flux (Jy)<br />
|-<br />
|U<br />
|0.36<br />
|0.15<br />
|1810<br />
|-<br />
|B<br />
|0.44<br />
|0.22<br />
|4260<br />
|-<br />
|V<br />
|0.55<br />
|0.16<br />
|3640<br />
|-<br />
|R<br />
|0.64<br />
|0.23<br />
|3080<br />
|-<br />
|I<br />
|0.79<br />
|0.19<br />
|2550<br />
|-<br />
|J<br />
|1.26<br />
|0.16<br />
|1600<br />
|-<br />
|H<br />
|1.60<br />
|0.23<br />
|1080<br />
|-<br />
|K<br />
|2.22<br />
|0.23<br />
|670<br />
|-<br />
|Ks<br />
|2.15<br />
|0.31<br />
|666.7<br />
|-<br />
|}<br />
(1 Jy = 1 Jansky = 10^-26 W Hz^-1 m^-2)<br />
<br />
<br />
There is another type of magnitude system called the AB magnitude system where Vega is not the standard, but rather every filter is DEFINED to have the same zero_point_flux of 3631 Jy for all filters in the AB system. The ugriz filters in the Kepler catalog are in the Sloan Digitized Sky Survey (SDSS) system which is an AB magnitude system.<br />
<br />
Central wavelengths of these filters are ...<br />
{| border = "1" style="text-align:center;"<br />
!u<br />
!g<br />
!r<br />
!i<br />
!z<br />
|-<br />
|0.355<br />
|0.469<br />
|0.617<br />
|0.748<br />
|0.893<br />
|}<br />
<br />
<br />
Finally, just to make things even more confusing, there are various versions of the filters (e.g., Johnson R vs Cousins R) that are similar but slightly different in wavelength or zero point flux or both. For our purposes, I would not worry so much about that.<br />
<br />
One more finally, in the KIC, you will see two filter D51 and GREDMAG - those are non-standard filters and finding conversions for those is difficult. You can collect them but I will need some time to think about how to use them.<br />
<br />
Also one more finally, I used the term flux. Actually, these conversions are from magnitude to FLUX DENSITY. A flux density is an amount of energy per time per area per unit wavelength or frequency (hence the per Hz in the units of Jansky) whereas a flux is an amount of energy per unit time per area over all wavelengths. The terminology is a detail that astronomers often use interchangeably - and often incorrectly.</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Filters&diff=8532Filters2012-02-20T02:15:29Z<p>Childers: Created page with "I found [http://www.astro.umd.edu/~ssm/ASTR620/mags.html this page] which was a helpful expansion on David's email of Feb. 11. Note howeve..."</p>
<hr />
<div>I found [http://www.astro.umd.edu/~ssm/ASTR620/mags.html this page] which was a helpful expansion on [[Filters#David's_Original_E-Mail|David's email of Feb. 11]]. Note however that the [http://www.astro.umd.edu/~ssm/ASTR620/mags.html#flux table for Photon Flux] has different central wavelengths for the AB filters than David did (the data for the Johnson filters all match).<br />
<br />
<!-- == Convert Johnson Magnitude to Janksy == --><br />
== David's Original E-Mail ==<br />
<br />
Dear Folks,<br />
<br />
As you know magnitudes are a logarithmic unit that runs backwards (i.e., brighter sources have smaller values). The magnitude scale is defined such that<br />
<br />
<code><big>magnitude = -2.5*log10(flux/zero_point_flux)</big></code><br />
<br />
where flux is the flux of the star and the zero_point_flux is the flux of a reference star DEFINED to have a magnitude = 0.0<br />
<br />
Magnitudes are useful handles on comparing the brightness of two or more sources within the same filter; i.e., source A has a magnitude of V=10 and source B has a magnitude of V=5 therefore source A is 100 times fainter). But in order to compare brightnesses of the SAME object at different filters or to compare other physical units (like the total luminosity), the magnitude scale needs to be converted to flux. For example, Vega is DEFINED to have a Johnson V=0 mag and a Johnson K = 0 mag; however, Vega is 5 times brighter in the optical (V) than it is in the infrared (K).<br />
<br />
And just to make things more complicated, there are actually two different kinds of magnitudes. There is the Johnson magnitude system (the one you are most familiar with). In this system, Vega is the standard where all magnitudes are compared to Vega which is DEFINED to have a magnitude = 0 in every filter. These filters typically include (and capitalization matters here) UBVRIJHK. In this system, the zero_point_flux for each filter changes, because the brightness of Vega changes with wavelength.<br />
<br />
<br />
{| border = "1" style="text-align:center;"<br />
!Filter <br />
!Central wave (microns) <br />
!Width wave (microns)<br />
!zero point flux (Jy)<br />
|-<br />
|U<br />
|0.36<br />
|0.15<br />
|1810<br />
|-<br />
|B<br />
|0.44<br />
|0.22<br />
|4260<br />
|-<br />
|V<br />
|0.55<br />
|0.16<br />
|3640<br />
|-<br />
|R<br />
|0.64<br />
|0.23<br />
|3080<br />
|-<br />
|I<br />
|0.79<br />
|0.19<br />
|2550<br />
|-<br />
|J<br />
|1.26<br />
|0.16<br />
|1600<br />
|-<br />
|H<br />
|1.60<br />
|0.23<br />
|1080<br />
|-<br />
|K<br />
|2.22<br />
|0.23<br />
|670<br />
|-<br />
|Ks<br />
|2.15<br />
|0.31<br />
|666.7<br />
|-<br />
|}<br />
(1 Jy = 1 Jansky = 10^-26 W Hz^-1 m^-2)<br />
<br />
<br />
There is another type of magnitude system called the AB magnitude system where Vega is not the standard, but rather every filter is DEFINED to have the same zero_point_flux of 3631 Jy for all filters in the AB system. The ugriz filters in the Kepler catalog are in the Sloan Digitized Sky Survey (SDSS) system which is an AB magnitude system.<br />
<br />
Central wavelengths of these filters are ...<br />
{| border = "1" style="text-align:center;"<br />
!u<br />
!g<br />
!r<br />
!i<br />
!z<br />
|-<br />
|0.355<br />
|0.469<br />
|0.617<br />
|0.748<br />
|0.893<br />
|}<br />
<br />
<br />
Finally, just to make things even more confusing, there are various versions of the filters (e.g., Johnson R vs Cousins R) that are similar but slightly different in wavelength or zero point flux or both. For our purposes, I would not worry so much about that.<br />
<br />
One more finally, in the KIC, you will see two filter D51 and GREDMAG - those are non-standard filters and finding conversions for those is difficult. You can collect them but I will need some time to think about how to use them.<br />
<br />
Also one more finally, I used the term flux. Actually, these conversions are from magnitude to FLUX DENSITY. A flux density is an amount of energy per time per area per unit wavelength or frequency (hence the per Hz in the units of Jansky) whereas a flux is an amount of energy per unit time per area over all wavelengths. The terminology is a detail that astronomers often use interchangeably - and often incorrectly.</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=Help:Contents&diff=8531Help:Contents2012-02-20T01:48:28Z<p>Childers: /* General wiki editing help */</p>
<hr />
<div>Here are some general semi-random bits of helpful documentation we've written or found.<br />
<br />
= Where can I find things? Where am I supposed to add things, or ask questions?=<br />
<br />
There is a LOT of stuff on this wiki, and we know it. For someone new, we do realize that it can be overwhelming. Here is a crash course to get started:<br />
<br />
* See the navigation bar on the left? You can use this to get to each of the main sections, or this page, from anywhere in the wiki. You can also use the search box to see if we have anything yet on your favorite section.<br />
* By all means, click around and see what we have. If you find a red link, it means that the destination you would reach, were you to click on that link, does not exist yet. Even some of the pages that do exist have spots that say "to be filled in more later" or similar text. This wiki is not "done" and it probably never will be -- it is a constantly evolving and changing forum.<br />
* Each of the pages we have is called (in wiki parlance) an "article." Each of the pages also has a "discussion" tab on the top left of each page. If that discussion tab is red, the so-called "talk page" doesn't exist yet. But, for several of the pages, that discussion tab is blue and the talk page does exist. If you click on the discussion tab, you might find a long or a short discussion about the contents of the main article. (Example: main article is [[Working_area_for_AAS_jan_2008_poster |this working area for writing our AAS posters]], and the discussion about it is [[Talk:Working_area_for_AAS_jan_2008_poster| here]]. See how the main article has introductory and summary information, but the discussion page has the back story, earlier versions, questions, interactions? that's the idea ....)<br />
* If you have questions about some of the things you find here, or you find things that you think are wrong, or should be changed, '''most likely, you should add your question or correction to the talk page''' to see if anyone else agrees or disagrees with you. (The exception would be simple typos - if you find a simple typo, by all means correct it.) There is general wiki editing help below, ''including instructions for signing your question when you enter it on the talk page.''<br />
* In order to find what has been going on lately on the wiki, click on "recent changes" on the menu bar on the left hand side. This will show you all of the most recent changes to the wiki, and through the options on the top, you can control how far back in time it goes & whether or not it shows your changes as well as everyone else's. You can also use the "diff" and "hist" links on each line to see exactly what that person changed when they edited that page.<br />
<br />
= Be polite. =<br />
<br />
Please:<br />
*Be polite.<br />
*Use good grammar.<br />
*Sign your questions or comments.<br />
<br />
<br />
= General wiki editing help =<br />
<br />
Consult the [http://meta.wikipedia.org/wiki/MediaWiki_User%27s_Guide User's Guide] for tons of information on using '''(including editing files with)''' the wiki software. [[Playground]] to experiment with formatting.<br />
<br />
* [http://www.mediawiki.org/wiki/Help:Formatting Formatting tags for editing pages]<br />
* [http://www.mediawiki.org/wiki/Help:Configuration_settings Configuration settings list]<br />
* [http://www.mediawiki.org/wiki/Help:FAQ MediaWiki FAQ]<br />
* [http://mail.wikipedia.org/mailman/listinfo/mediawiki-announce MediaWiki release mailing list]<br />
<br />
= Guidelines for posting a comment =<br />
<br />
Please start a new thread if you are starting a new comment.<br />
<br />
<br />
--[[User:Danielle|Dani]] 10:53, 4 December 2007 (PST)When posting, rather than typing your name and time, simply click the icon above the Subject/Headling square that looks like a squiggle. It is the second icon from the right. Click that before you start your post, it will post your name date and time for you. and then at the end of the post, simply type [end]<br />
<br />
--[[User:Spuck|Spuck]] 12:08, 4 December 2007 (PST) This is a very useful tool, so please use it. This is what it looks like on your editing screen:<br />
<br />
[[Image:timestamp.jpg]] [end]<br />
<br />
--[[User:Danielle|DanielleYeager]] 07:34, 5 December 2007 (PST) if you go into your preferences and change your 'nickname' it changes what comes up as your name for your signature.[end]<br />
<br />
<br />
=Guidelines for posting a file=<br />
<br />
Here is a step-by-step example on how to post a file. Be sure that you are on the right page for what you want to do, and name your file something other than this example filename -- if you pick a filename that already exists, it will link to that existing file.<br />
<br />
Example posting of a contribution for the 2008 Jan AAS poster.<br />
<br />
#Follow the link to here: https://coolwiki.ipac.caltech.edu/index.php/Working_area_for_AAS_jan_2008_poster This is the 'overview' page.<br />
#For contributed pieces for the poster, click on the "discussion" tab on the top left. It will take you here: https://coolwiki.ipac.caltech.edu/index.php/Talk:Working_area_for_AAS_jan_2008_poster<br />
#Log in if you haven't already.<br />
#Scroll down past the large graphic and see the conversations already taking place about what to put in the poster. Find the end of the conversation where you can add your contribution.<br />
#Edit the page.<br />
#Scroll down to the end of the conversation where you can add your contribution.<br />
#OPTION 1: if you have plain text to contribute:<br />
##type the following in the page where you want to make your addition.<br />
Note that the first set of characters can be obtained by clicking on the 'signature' button as demonstrated above, but may not appear when you are using safari. However, you can just type the characters as they appear here, and it will automatically put in your signature and timestamp.<br />
-begin example-<br />
<pre><br />
--~~~~ Hi, here is what Esseim and I have been working on:<br />
(type in or copy-and-paste your text contribution here)<br />
</pre><br />
-end example-<br />
#OPTION 2: if you have a jpg file beyond plain text:<br />
##type the following in the page where you want to make your addition.<br />
Note that the first set of characters can be obtained by clicking on the 'signature' button as demonstrated above, but may not appear when you are using safari. However, you can just type the characters as they appear here, and it will automatically put in your signature and timestamp.<br />
-begin example-<br />
<pre><br />
--~~~~ Hi, here is what Esseim and I have been working on:<br />
[[Image:ourdraft.jpg]]<br />
</pre><br />
-end example-<br />
#OPTION 3: if you have a ppt file or anything else:<br />
##type the following in the page where you want to make your addition.<br />
Note that the first set of characters can be obtained by clicking on the 'signature' button as demonstrated above, but may not appear when you are using safari. However, you can just type the characters as they appear here, and it will automatically put in your signature and timestamp.<br />
-begin example-<br />
<pre><br />
--~~~~ Hi, here is what Esseim and I have been working on:<br />
[[Media:ourdraft.ppt]]<br />
</pre><br />
-end example-<br />
ALL OPTIONS CONTINUE HERE:<br />
#Whichever option you use, then click the "save page" button to save your changes! <br />
#When you save your edits, the bracketed will show up as a red link on the page. Click on the link. It will then ask you to upload the file. NB: if your link does not show up as red, it is linking to an existing file on the server, and you need to find a new filename for your file. Go back and edit the page and change the filename.<br />
#Find the file on your local disk and upload it. It might give you a warning regarding file size. tell it to ignore the warning and upload anyway. <br />
#After you upload the file, it will give you a page that includes among several other things a link that is worded something to the effect of "what links here". Click on that link to be taken back to the talk page which has the embedded link to your image or file.</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=UBOKO_Current_Research_Activities&diff=8530UBOKO Current Research Activities2012-02-20T01:30:19Z<p>Childers: /* BOKO Spring work */</p>
<hr />
<div>=BOKO Suggested Reading List=<br />
<br />
Things teachers and students should read.<br />
<br />
=BOKO Proposal=<br />
[[Proposal Outline]]<br />
<br />
=BOKO Spring work=<br />
<br />
[[Starting Email from Sally - 15 Jan 2012]]<br />
<br />
[[Starting Email from Ciardi - 20 Jan 2012]]<br />
<br />
[[Telecon Sunday 22 Jan 2012]]<br />
<br />
[[Telecon Monday 06 Feb 2012]]<br />
<br />
[[Kepler]] Add thoughts and tips about Kepler here.<br />
<br />
[[Galex]] Add thoughts and tips about using Galex here.<br />
<br />
[[SIMBAD]] Add thoughts and tips about using SIMBAD here.<br />
<br />
[[Filters]] Add thoughts and tips about using data from various filters here.</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=SIMBAD&diff=8529SIMBAD2012-02-19T23:33:47Z<p>Childers: /* Downloading Magnitudes from a List of Identifiers to a Spreadsheet */</p>
<hr />
<div><br />
== Downloading Magnitudes from a List of Identifiers to a Spreadsheet ==<br />
<br />
# '''Start on the [http://simbad.u-strasbg.fr/simbad/ SIMBAD home page.]''' Look on the left for <font color="red">''Queries''</font>, and then underneath that click on ''by identifier''.<br />
# '''Set Output Options'''<br />
## Click on '''Output Options''', which is in a yellow box on the right-hand side of the '''''other query modes''''' row along the top. A new browser tab will open.<br />
## Set the '''Output Format''' in the top row.<br />
### Choose '''ASCII (;-separator for spreadsheet)''' from the drop-down menu.<br />
### Check '''file output'''.<br />
## Make changes to the '''List Display''' column.<br />
### Make sure '''Identifier''' is checked.<br />
### Make sure '''Fluxes/Magnitudes''' is checked<br />
### You must also check the '''individual filters''' in the right-hand cells of the Fluxes/Magnitudes row. You have nothing to lose by clicking all of them.<br />
### In general, uncheck all other rows, unless you are suspicious about your target list and would like some extra columns in your spreadsheet to act as a reality check.<br />
## Click the '''SAVE''' button at the bottom to set a browser cookie and save your changes.<br />
# '''Query a List of Identifiers''' is on the bottom half of the original SIMBAD query browser tab.<br />
## Prepare a '''.txt''' Notepad file containing only SIMBAD acceptable identifiers without a header. Chances are if you got your list of identifiers from a catalog, you'll be okay. <br />
## Click '''Choose File''' and browse to your text file.<br />
## Check '''''list display'''''.<br />
## Check '''Submit File'''.<br />
# '''A .csv file will begin downloading automatically.'''<br />
::* Since semicolon is not the default delimiter in Excel, either use File > Open and then Data > Text to Columns, or use Data > Import External Data > Import Data.<br />
::* The first few rows of the file identify and timestamp the query<br />
::* Missing magnitudes for a given filter are shown with a tilde (~) symbol.<br />
::* Identifiers from the uploaded list that SIMBAD couldn't parse are listed separately at the end.<br />
<br />
--[[User:Childers|Childers]] 15:21, 19 February 2012 (PST)</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=SIMBAD&diff=8528SIMBAD2012-02-19T23:32:40Z<p>Childers: /* Downloading Magnitudes from a List of Identifiers to a Spreadsheet */</p>
<hr />
<div><br />
== Downloading Magnitudes from a List of Identifiers to a Spreadsheet ==<br />
<br />
# '''Start on the [http://simbad.u-strasbg.fr/simbad/ SIMBAD home page.]''' Look on the left for <font color="red">''Queries''</font>, and then underneath that click on ''by identifier''.<br />
# '''Set Output Options'''<br />
## Click on '''Output Options''', which is in a yellow box on the right-hand side of the '''''other query modes''''' row along the top. A new tab will open.<br />
## Set the '''Output Format''' in the top row.<br />
### Choose '''ASCII (;-separator for spreadsheet)''' from the drop-down menu.<br />
### Check '''file output'''.<br />
## Make changes to the '''List Display''' column.<br />
### Make sure '''Identifier''' is checked.<br />
### Make sure '''Fluxes/Magnitudes''' is checked<br />
### You must also check the '''individual filters''' in the right-hand cells of the Fluxes/Magnitudes row. You have nothing to lose by clicking all of them.<br />
### In general, uncheck all other rows, unless you are suspicious about your target list and would like some extra columns in your spreadsheet to act as a reality check.<br />
## Click the '''SAVE''' button at the bottom to set a browser cookie and save your changes.<br />
# '''Query a List of Identifiers''' is on the bottom half of the page.<br />
## Prepare a '''.txt''' Notepad file containing only SIMBAD acceptable identifiers without a header. Chances are if you got your list of identifiers from a catalog, you'll be okay. <br />
## Click '''Choose File''' and browse to your text file.<br />
## Check '''''list display'''''.<br />
## Check '''Submit File'''.<br />
# '''A .csv file will begin downloading automatically.'''<br />
::* Since semicolon is not the default delimiter in Excel, either use File > Open and then Data > Text to Columns, or use Data > Import External Data > Import Data.<br />
::* The first few rows of the file identify and timestamp the query<br />
::* Missing magnitudes for a given filter are shown with a tilde (~) symbol.<br />
::* Identifiers from the uploaded list that SIMBAD couldn't parse are listed separately at the end.<br />
<br />
--[[User:Childers|Childers]] 15:21, 19 February 2012 (PST)</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=SIMBAD&diff=8527SIMBAD2012-02-19T23:25:28Z<p>Childers: /* Downloading Magnitudes from a List of Identifiers to a Spreadsheet */</p>
<hr />
<div><br />
== Downloading Magnitudes from a List of Identifiers to a Spreadsheet ==<br />
<br />
# '''Start on the [http://simbad.u-strasbg.fr/simbad/ SIMBAD home page.]''' Look on the left for <font color="red">''Queries''</font>, and then underneath that click on ''by identifier''.<br />
# '''Set Output Options'''<br />
## Click on '''Output Options''', which is in a yellow box on the right-hand side of the '''''other query modes''''' row along the top. A new tab will open.<br />
## Set the '''Output Format''' in the top row.<br />
### Choose '''ASCII (;-separator for spreadsheet)''' from the drop-down menu.<br />
### Check '''file output'''.<br />
## Make changes to the '''List Display''' column.<br />
### Make sure '''Identifier''' is checked.<br />
### Make sure '''Fluxes/Magnitudes''' is checked<br />
### You must also check the '''individual filters''' in the right-hand cells of the Fluxes/Magnitudes row. You have nothing to lose by clicking all of them.<br />
### In general, uncheck all other rows, unless you are suspicious about your target list and would like some extra columns in your spreadsheet to act as a reality check.<br />
## Click the '''SAVE''' button at the bottom to set a browser cookie and save your changes.<br />
# '''Query a List of Identifiers''' is on the bottom half of the page.<br />
## Prepare a '''.txt''' Notepad file containing only SIMBAD acceptable identifiers without a header. Chances are if you got your list of identifiers from a catalog, you'll be okay. <br />
## Click '''Choose File''' and browse to your text file.<br />
## Check '''''list display'''''.<br />
## Check '''Submit File'''.<br />
# '''A .csv file will begin downloading automatically.'''<br />
::* If you are using Excel, then you'll need to use Data > Text to Columns and explicitly tell it that you are using semi-colons as a delimiter.<br />
::* The first few rows of the file identify and timestamp the query<br />
::* Missing magnitudes for a given filter are shown with a tilde (~) symbol.<br />
::* Identifiers from the uploaded list that SIMBAD couldn't parse are listed separately at the end.<br />
<br />
--[[User:Childers|Childers]] 15:21, 19 February 2012 (PST)</div>Childershttps://vmcoolwiki.ipac.caltech.edu/index.php?title=SIMBAD&diff=8526SIMBAD2012-02-19T23:21:03Z<p>Childers: Created page with " == Downloading Magnitudes from a List of Identifiers to a Spreadsheet == # '''Start on the [http://simbad.u-strasbg.fr/simbad/ SIMBAD home page.]''' Look on the left for <f..."</p>
<hr />
<div><br />
== Downloading Magnitudes from a List of Identifiers to a Spreadsheet ==<br />
<br />
# '''Start on the [http://simbad.u-strasbg.fr/simbad/ SIMBAD home page.]''' Look on the left for <font color="red">''Queries''</font>, and then underneath that click on ''by identifier''.<br />
# '''Set Output Options'''<br />
## Click on '''Output Options''', which is in a yellow box on the right-hand side of the '''''other query modes''''' row along the top. A new tab will open.<br />
## Set the '''Output Format''' in the top row.<br />
### Choose '''ASCII (;-separator for spreadsheet)''' from the drop-down menu.<br />
### Check '''file output'''.<br />
## Make changes to the '''List Display''' column.<br />
### Make sure '''Identifier''' is checked.<br />
### Make sure '''Fluxes/Magnitudes''' is checked<br />
### You must also check the '''individual filters''' in the right-hand cells of the Fluxes/Magnitudes row. You have nothing to lose by clicking all of them.<br />
### In general, uncheck all other rows, unless you are suspicious about your target list and would like some extra columns in your spreadsheet to act as a reality check.<br />
## Click the '''SAVE''' button at the bottom to set a browser cookie and save your changes.<br />
# '''Query a List of Identifiers''' is on the bottom half of the page.<br />
## Prepare a '''.txt''' Notepad file containing only SIMBAD acceptable identifiers without a header. Chances are if you got your list of identifiers from a catalog, you'll be okay. <br />
## Click '''Choose File''' and browse to your text file.<br />
## Check '''''list display'''''.<br />
## Check '''Submit File'''.<br />
# '''A .csv file will begin downloading automatically.'''<br />
::* The first few rows of the file identify and timestamp the query<br />
::* Missing magnitudes for a given filter are shown with a tilde (~) symbol.<br />
::* Identifiers from the uploaded list that SIMBAD couldn't parse are listed separately at the end.<br />
<br />
--[[User:Childers|Childers]] 15:21, 19 February 2012 (PST)</div>Childers