No Photon Left Behind: Finding Heavily Obscured AGN at Cosmic Noon in the Chandra Deep Fields
Abstract
Population synthesis models of actively accreting super-massive black holes (or active galactic nuclei -- AGN) predict a large fraction must grow behind dense, obscuring screens of gas and dust. X-ray surveys provide some of the most complete and unbiased samples of AGN, but it is thought that even the deepest X-ray surveys to date are missing large portions of the obscured AGN parameter space -- in particular, less luminous, heavily obscured AGN at z > 0.5. In this talk I will present our recent work on uncovering demographically plentiful, but observationally rare populations of heavily obscured AGN (N _{H} > 10 24 cm -2, 0.5 < z < 3.0). I will present two different methods (1) Combining 2-10 keV detected X-ray sources with model independent, direct estimates of the 5 micron luminosity, and (2) Using joint spectral analysis to estimate the N _{H} of obscured AGN candidates identified via multi-wavelength methods. The uncovered populations of obscured AGN identified with these methods are in strong agreement with space densities derived from X-ray background models with higher fractions of heavily obscured AGN This work finds that even some of the lowest X-ray flux sources may contain enough spectral information to identify populations of X-ray faint, heavily obscured AGN at cosmic noon - thus maximizing the potential of < 10 keV X-ray past, present and future surveys to detect and identify less-luminous heavily obscured AGN throughout cosmic time.
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.1814L