C-WAYS source matching work
Introduction
Several people have done prior studies in BRC 27, BRC 34, and BRC 38 before. You worked hard to find all of these articles in the context of the proposal. Now we actually have to do the work of figuring out which sources are which in all the papers - are the sources called out in paper 1 the same or different sources as paper 2, etc., until all the papers are exhausted, and we have a complete catalog of all the previously studied sources in the region.
The thing that makes this complicated is that, even though everyone is reporting in RA and Dec, not everyone is using exactly the same system (some are 1950 coordinates and some are 2000 coordinate), and not everyone has the same coordinate accuracies (some are working off of photographic plates, and some are working off large-format CCDs). This is where it gets tricky, and where you have to apply your brain! Spitzer, WISE, and 2MASS are all using exactly the same, high-accuracy coordinate system. We need to update the old coordinates by comparing what the old papers say to the 2mass data, as well as fold in the objects with newer coordinates into our collection of sources.
An analogy
Review the differences between the 1950 and 2000 coordinate systems. REMINDER: THE STARS ARE NOT MOVING. The coordinate system is moving, not the stars. (Well, the stars may really be moving, but we don't have that information, and the size of any such motion will be on the order of a tenth of an arcsec or less; the change due to coordinates is much greater.) An analogy can provide an example. Through Google Maps, I can see that there is a Baskin Robbins near Ms. Linahan's school (from the NITARP 2011 class). I can give you the position of that Baskin Robbins in any of a number of ways:
- 346 North Lake St, Mundelein, IL
- 8 long blocks roughly west of the school
- 4 minutes west of your school (if you drive)
- 20 minutes west of your school (if you walk)
- latitude 42.269711, longitude -88.004308
Or, I could be really pathological and/or vague and say:
- the 3rd oldest Baskin Robbins in Mundelein (NB: i'm just making this up)
- the 5th oldest ice cream store in Munelein (NB: i'm just making this up)
- An ice cream store on Lake, south of Loch Lomond
Are the coordinates different in these systems? Yes, but they are pointing to the same physical location. Is the Baskin Robbins really moving? No.
That is what is going on in these BRCs. The B1950 coordinates and the J2000 coordinates are different coordinate systems, and we are trying to translate one into the other, e.g., translate each of the bullets in the above into "latitude 42.269711, longitude -88.004308". The added complication here is that the previous authors were not working in particularly precise coordinate systems. That's true of the list above too. Given the list above, your first step in finding this store might be to identify all the ice cream stores on Lake, south of Loch Lomond, figure out how old some of them are, and then, having identified this one, then somehow obtain its address in house numbers (346 North Lake St) and then work on converting that to lat/long (42.269711, -88.004308).
So that is what we have to do with the BRCs.
