The Obscured Fraction of Luminous X-ray AGN at the Peak of the Cosmic Accretion Growth
Abstract
X-ray selected AGN studies indicate that the fraction of obscured AGN increasing with increasing redshift, and suggests that significant part of the accretion growth occurs behind obscuring material in the early universe. Here, we investigate the obscured fraction of highly accreting X-ray AGN at around the peak of SMBH growth utilizing the wide and deep X-ray and optical/IR imaging dataset to construct a PSF-convolved photometric catalog covering from u^*-band to 4.5 μ m. The catalog is matched with the XMM-SERVS point-source catalog and for the X-ray AGN, the photometric redshift, column density, and 2-10 keV AGN luminosity was estimated. Using a sample of 333 2-10 keV detected AGN at redshift more than 2, we estimate the obscured fraction (log N_H>22) using a maximum-likelihood method assuming a parametric X-ray luminosity function. We estimate that 70 ± 4% of luminous quasars (log L_X >44.5) above redshift 2 are obscured, 3 times larger than in the local universe. The results may be indicative of an increase contribution of obscuration due to merger events or gas fraction in the nuclear regions at high redshift. Both of the obscured and less-obscured AGN show wide range of SED and morphology in the UV to IR range, which may reflect wide variety in the properties of their host galaxies.
- Publication:
-
44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.1842V