The Quest for a Complete Census of AGN Activity

2006/12/18 by D. M. Alexander, Alexander, D. M.
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph

paper · pdf · doi:10.48550/arxiv.astro-ph/0612497

8 pages, 3 figs; contribution for IR diagnostics of Galaxy Evolution Spitzer conference in Pasadena; bibtex references added

arxiv created 2007/01/25 · arxiv updated 2009/12/01

Abstract

Deep X-ray surveys provide the most efficient identification of Active Galactic Nuclei (AGN) activity. However, recent evidence has indicated that the current <10 keV surveys do not detect the most heavily obscured AGNs. Here we explore whether the X-ray undetected AGN population can be identified within the ultra-deep Spitzer survey of the GOODS-N field using X-ray stacking techniques. We find evidence for AGN activity in the Spitzer dataset and the strongest and hardest X-ray signal is produced by galaxies with starburst-like infrared spectral slopes and median properties of z~0.8 and L_IR~10¹¹ L_solar. The stacked X-ray properties suggest that obscured AGN activity is present in these sources, with a median X-ray spectral slope of Gamma~1 and L_X~10⁴² erg/s. These overall properties are consistent with the obscured AGN population expected to produce the unresolved X-ray background.

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