The Obscured Fraction of Quasars at Cosmic Noon

Bovornpratch Vijarnwannaluk, Masayuki Akiyama, Malte Schramm, Yoshihiro Ueda, Yoshiki Matsuoka, Yoshiki Toba, Marcin Sawicki, Stephen Gwyn, Janek Pflugradt

研究成果: Article査読


Statistical studies of X-ray selected active galactic nuclei (AGN) indicate that the fraction of obscured AGN increases with increasing redshift, and the results suggest that a significant part of the accretion growth occurs behind obscuring material in the early universe. We investigate the obscured fraction of highly accreting X-ray AGN at around the peak epoch of supermassive black hole growth utilizing the wide and deep X-ray and optical/IR imaging data sets. A unique sample of luminous X-ray selected AGNs above z > 2 was constructed by matching the XMM-SERVS X-ray point-source catalog with a point-spread function convolved photometric catalog covering the u*-4.5 μm bands. Photometric redshift, hydrogen column density, and 2-10 keV AGN luminosity of the X-ray selected AGN candidates were estimated. Using the sample of 306 2-10 keV detected AGN at above redshift 2, we estimate the fraction of AGN with log N H ( cm − 2 ) > 22 , assuming parametric X-ray luminosity and absorption functions. The results suggest that 76 − 3 + 4 % of luminous quasars ( log L X ( erg s − 1 ) > 44.5 ) above redshift 2 are obscured. The fraction indicates an increased contribution of obscured accretion at high redshift than that in the local universe. We discuss the implications of the increasing obscured fraction with increasing redshift based on the AGN obscuration scenarios, which describe obscuration properties in the local universe. Both the obscured and unobscured z > 2 AGN show a broad range of SEDs and morphology, which may reflect the broad variety of host galaxy properties and physical processes associated with the obscuration.

ジャーナルAstrophysical Journal
出版ステータスPublished - 2022 12月 1

ASJC Scopus subject areas

  • 天文学と天体物理学
  • 宇宙惑星科学


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