S. V. Ramirez (1), R. G. Arendt (2), K. Sellgren (3), S. R. Stolovy (1), A. Cotera (4), H. A. Smith (5), and F. Yusef-Zadeh (6)
ApJS, 2008, in press (astro-ph/0709.3113)
We have obtained Spitzer/IRAC observations of the central 2.0 degrees X 1.4 degrees (~280 X 200 pc) of the Galaxy at 3.6 - 8.0 microns. A point source catalog of 1,065,565 objects is presented. The catalog includes magnitudes for the point sources at 3.6, 4.5, 5.8, and 8.0 microns, as well as JHKs photometry from 2MASS. The point source catalog is confusion limited with average limits of 12.4, 12.1, 11.7, and 11.2 magnitudes for [3.6], [4.5], [5.8], and [8.0], respectively. We find that the confusion limits are spatially variable because of stellar surface density, background surface brightness level, and extinction variations across the survey region. The overall distribution of point source density with Galactic longitude and latitude is essentially constant, but structure does appear when sources of different magnitude ranges are selected. Bright stars show a slow decreasing gradient with Galactic longitude, and a steep decreasing gradient with Galactic latitude, with a peak at the position of the Galactic Center. From IRAC color-magnitude and color-color diagrams, we conclude that most of the point sources in our catalog have IRAC magnitudes and colors characteristic of red giant and AGB stars.
(1) Infrared Processing and Analysis Center, Caltech
(2) CRESST/UMBC/GSFC
(3) Ohio State University
(4) SETI Institute
(5) Harvard-Smithsonian Center for Astrophysics
(6) Northwestern University
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Revised: 2007 October 2 (ks)