Point sources from a Spitzer IRAC survey of the Galactic Center

Abstract

We have obtained Spitzer IRAC observations of the central 2.0° × 1.4° (~280 × 200 pc) of the Galaxy at 3.6-8.0 μm. 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 μm, as well as JHK_s photometry from Two Micron All Sky Survey (2MASS). The point-source catalog is confusion limited with average limits of 12.4, 12.1, 11.7, and 11.2 mag 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 latitude and longitude is essentially constant, but structure does appear when sources of different magnitude ranges are selected. Bright stars show a steep decreasing gradient with Galactic latitude and a slow decreasing gradient with Galactic longitude, 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 asymptotic giant branch (AGB) stars.