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D. Stern, P. Eisenhardt, V. Gorjian (JPL/Caltech), C.S. Kochanek (OSU), D. Eisenstein (Steward), P. Barmby (CfA), M. Brodwin (JPL/Caltech), M.J.I. Brown (Princeton), N. Caldwell (CfA), R. Cool (Steward), A. Dey (NOAO), P. Green (CfA), B.T. Jannuzi (NOAO), S. Murray, M.A. Pahre, S.P. Willner (CfA)
Mid-infrared photometry provides a robust technique for identifying active galaxies. Mirroring the tendency of AGN to be bluer than galaxies in the ultraviolet, where galaxies (and stars) sample the blue, rising portion of stellar spectra, AGN tend to be redder than galaxies in the mid-infrared, where galaxies sample the red, falling portion of the stellar spectra. We report on Spitzer Space Telescope mid-infrared colors, derived from the IRAC Shallow Survey, of nearly 10,000 spectroscopically-identified sources from the AGN and Galaxy Evolution Survey. Based on this spectroscopic sample, we find that simple mid-infrared color criteria provide remarkably robust separation of active galaxies from normal galaxies and Galactic stars, with over 80% completeness and less than 20% contamination. Considering only broad-lined AGN, these mid-infrared color criteria identify over 90% of spectroscopically-identified quasars and Seyfert 1s. Applying these color criteria to the full imaging data set, we discuss the implied surface density of AGN and find evidence for a large population of optically-obscured active galaxies.
The author(s) of this abstract have provided an email address for comments about the abstract: stern@zwolfkinder.jpl.nasa.gov
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.