Color-Color Analysis of GLIMPSE Point Sources

Daniel Capellupo, University of Rochester
Adviser: Ed Churchwell, University of Wisconsin - Madison

4. SIMBAD Searches

My next step was to take the galactic coordinates for these mystery objects and search the SIMBAD database to see if any of these objects have been identified by another catalog. I actually did this three times. The first time, I had selected smaller circles on the color-color diagram, and the SIMBAD search resulted in very few matches. Based on the positions, and their errors, I could identify no match to any of the lower peak objects and fewer than ten matches for the upper peak objects. So, I decided to use two larger circles (the ones shown on the color-color plot), and the SIMBAD search on the resulting list of objects again returned no results for the lower peak and ten matches to upper peak objects. About a week later, I noticed a problem in SIMBAD. For some reason, certain galactic coordinates are simply not recognized by SIMBAD and return zero results even if a very large search radius, like one degree, is selected. However, when I went back into the catalog and retrieved the right ascension and declination for an object whose galactic coordinates had not been recognized by SIMBAD, I did get a result.

So I did a second SIMBAD search on the objects from the two enlarged circles on the color-color diagram, and I got about twice the number of potential matches as before. Whereas in the previous SIMBAD search only 18 of the lower peak objects had a SIMBAD object within a 10 arcsec radius, in this last SIMBAD search 40 lower peak objects had a SIMBAD object within a 10 arcsec radius. Similarly, 45 upper peak objects had a SIMBAD object within a 10 arcsec radius in the previous search, and 102 did in the last search.

However, only 1 out of the 40 potential matches for the lower peak could actually be determined as a match. That is 1 out of 8971 objects.

For the upper peak, on the other hand, 23 out of the 102 potential matches were determined to be actual matches to an upper peak object. That is 23 out of 6472 objects.

5. Results

The following table shows the results of the SIMBAD search for the Upper Peak:

The results for the Lower Peak: 1 YSO

6. Conclusions

1. Upper Peak:
   • There is a collection of different objects for the lower peak; however, they all tend to be bright, young sources.
   • One reason the number of matches is so small is that these other surveys in the above table only cover very small patches of the sky. For example, the MS98 catalog only covers a 6 square-degree area, as opposed to GLIMPSE which covers about 220 square degrees.
2. Lower Peak:
   • It appears that we have stumbled upon a group of objects that has not been studied before.
   • The ISOGAL-P catalog, for example, did not pick out YSOs from the densest regions of the GLIMPSE survey. They only looked on the outside of the massive star formation regions.
   • However, we do still believe that these are protostars or some sort of young stars.