Comoving Space Density and Obscured Fraction of High-Redshift Active Galactic Nuclei in the Subaru/{\it XMM-Newton} Deep Survey

Abstract

We study the comoving space density of X-ray-selected luminous active galactic nuclei (AGNs) and the obscured AGN fraction at high redshifts ($3<z<5$) in the Subaru/{\it XMM-Newton} Deep Survey (SXDS) field. From an X-ray source catalog with high completeness of optical identification thanks to deep optical images, we select a sample of 30 AGNs at $z>3$ with intrinsic (de-absorbed and rest-frame 2--10 keV) luminosities of $L_{\mathrm{X}}=10^{44-45}$ erg s${}^{-1}$ detected in the 0.5--2 keV band, consisting of 20 and 10 objects with spectroscopic and photometric redshifts, respectively. Utilizing the $1/V_{\max }$ method, we confirm that the comoving space density of luminous AGNs decreases with redshift above $z>3$. When combined with the {\it Chandra}-COSMOS result of Civano et al.\ (2011), the density decline of AGNs with $L_{\mathrm{X}}=10^{44-45}$ erg s${}^{-1}$ is well represented by a power law of $(1+z{)}^{-6.2\pm 0.9}$. We also determine the fraction of X-ray obscured AGNs with $N_{\mathrm{H}}>10^{22}$ cm${}^{-2}$ in the Compton-thin population to be 0.54${}_{-0.19}^{+0.17}$, by carefully taking into account observational biases including the effects of photon statistics for each source. This result is consistent with an independent determination of the type-2 AGN fraction based on optical properties, for which the fraction is found to be 0.59$\pm$0.09. Comparing our result with that obtained in the local Universe, we conclude that the obscured fraction of luminous AGNs increases significantly from $z=0$ to $z>3$ by a factor of 2.5$\pm$1.1.

12 pages, 12 figures, 1 table. Accepted for publication in ApJ

References in corpus (15)

• The Cosmic Evolution Survey (COSMOS) -- Overview
• EAZY: A Fast, Public Photometric Redshift Code
• A luminous quasar at a redshift of z = 7.085
• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• The Chandra COSMOS Survey, I: Overview and Point Source Catalog
• Absorption Properties and Evolution of Active Galactic Nuclei
• The XMM-Newton wide-field survey in the COSMOS field: I. Survey description
• The Subaru/XMM-Newton Deep Survey (SXDS) - II. Optical Imaging and Photometric Catalogs
• The Luminosity Function of X-ray Selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift
• The Multiwavelength Survey by Yale-Chile (MUSYC): Deep Medium-Band optical imaging and high quality 32-band photometric redshifts in the ECDF-S
• The Subaru/XMM-Newton Deep Survey (SXDS): III. X-Ray Data
• The Evolution of Obscuration in AGN
• Evolution of the Quasar Luminosity Function Over 3 < z < 5 in the COSMOS Survey Field
• High redshift quasars in the COSMOS survey: the space density of z>3 X-ray selected QSOs
• The XMM-Newton Serendipitous Survey. VI. The X-ray Luminosity Function

Cited by in corpus (24)

• Toward the Standard Population Synthesis Model of the X-Ray Background: Evolution of X-Ray Luminosity and Absorption Functions of Active Galactic Nuclei Including Compton-Thick Populations
• Cosmic X-ray Surveys of Distant Active Galaxies: The Demographics, Physics, and Ecology of Growing Supermassive Black Holes
• High-redshift AGN in the Chandra Deep Fields: the obscured fraction and space density of the sub-$L_{\ast }$ population
• Compton thick active galactic nuclei in Chandra surveys
• The Quasar Luminosity Function at Redshift 4 with Hyper Suprime-Cam Wide Survey
• The Hard X-Ray Luminosity Function of High-Redshift ($3<z\lesssim 5$) Active Galactic Nuclei
• The X-ray luminosity function of Active Galactic Nuclei in the redshift interval z=3-5
• X-ray spectral analyses of AGNs from the 7Ms Chandra Deep Field-South survey: the distribution, variability, and evolution of AGN's obscuration
• The deepest X-ray view of high-redshift galaxies: constraints on low-rate black-hole accretion
• Black hole mass and Eddington ratio distribution functions of X-ray selected broad-line AGNs at z~1.4 in the Subaru XMM-Newton Deep Field
• The Chandra Deep Fields: Lifting the Veil on Distant Active Galactic Nuclei and X-Ray Emitting Galaxies
• First constraints on the AGN X-ray luminosity function at $z\sim 6$ from an eROSITA-detected quasar
• The Largest X-ray Selected Sample of z>3 AGNs: C-COSMOS & ChaMP
• High redshift AGNs and HI reionisation: limits from the unresolved X-ray background
• The Subaru-XMM-Newton Deep Survey (SXDS) VIII.: Multi-wavelength Identification, Optical/NIR Spectroscopic Properties, and Photometric Redshifts of X-ray Sources
• The 2-10 keV unabsorbed luminosity function of AGN from the XMM-Newton LSS, CDFS and COSMOS surveys
• On the contribution of active galactic nuclei to reionization (Research Note)
• AGN X-ray luminosity function and absorption function in the Early Universe ($3\le z\le 6$)
• The Obscured Fraction of Quasars at Cosmic Noon
• A graphical analysis of the systematic error of classical binned methods in constructing luminosity functions
• XXL-HSC: An updated catalogue of high-redshift ($z⩾3.5$) X-ray AGN in the XMM-XXL northern field. Constraints on the bright end of the soft logN-logS
• On the Evolution of High-Redshift Active Galactic Nuclei
• Astrophysical interpretation of small-scale neutrino angular correlation searches with IceCube
• BASS XXX: Distribution Functions of DR2 Eddington-ratios, Black Hole Masses, and X-ray Luminosities