Oral Presentation

The obscured fraction of quasars at redshift 2-5

Author(s): Bovornpratch Vijarnwannaluk (Tohoku U.), Masayuki Akiyama (Tohoku U.), Malte Schramm (Saitama U.), Yoshihiro Ueda (Kyoto U.), Yoshiki Matsuoka (Ehime U.) Yoshiki Toba (Kyoto U.)

Presenter: Bovornpratch Vijarnwannaluk (Tohoku Univerisity)

We investigate the X-ray obscured fraction of quasars above redshift two within the HSC-SSP XMM-LSS deep field. A PSF-convolved photometric catalog was constructed using deep optical/IR imaging datasets taken in 11-photometric bands covering from u* to 4.6 micron. The catalog was matched with the XMM-SERVS point source catalog (Chen et al. 2018) and the photometric redshift, column density, and 2-10 keV AGN luminosity was estimated. The sample of 715 high-z AGN above redshift two was selected based on the best available redshift information. We assumed a parametric model and perform a maximum-likelihood fitting to estimate the obscured fraction at high redshift. Our results suggest that the obscured fraction increases from the local universe. Based on the best-fit parameters, 0.38±0.03 of luminous quasars above redshift two are obscured. This corresponds to approximately 76% of the Compton-thin AGN population. In addition, we investigate the correspondence between the rest-frame colors and X-ray obscuration. We find a weak correspondence between SED shape and X-ray obscuration suggesting that the host galaxy can significantly influence the SED and colors of X-ray obscured AGN causing them to be missed by typical Type-1 AGN color selection.