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Title: COMOVING SPACE DENSITY AND OBSCURED FRACTION OF HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI IN THE SUBARU/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/XMM-Newton Deep Survey 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{sub X} = 10{sup 44-45} erg s{sup -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{sub max} method, we confirm that the comoving space density of luminous AGNs decreases with redshift above z > 3. When combined with the Chandra-COSMOS result of Civano et al., the density decline of AGNs with L{sub X} = 10{sup 44-45} erg s{sup -1} is well represented by a power law of (1 + z){sup -6.2{+-}0.9}. We also determine the fraction of X-ray obscured AGNs with N{sub H} > 10{sup 22} cm{sup -2} in the Compton-thin population to be 0.54{sup +0.17}{sub -0.19}, by carefully taking into account observational biases including the effects of photon statistics for each source. This result is consistent with anmore » independent determination of the type-2 AGN fraction based on optical properties, for which the fraction is found to be 0.59 {+-} 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 {+-} 1.1.« less

Authors:
;  [1];  [2]
  1. Department of Astronomy, Kyoto University, Oiwake-cho, Sakyo-ku, Kyoto (Japan)
  2. Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai (Japan)
Publication Date:
OSTI Identifier:
22092082
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 758; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; CATALOGS; DENSITY; GALAXY NUCLEI; KEV RANGE; LUMINOSITY; PHOTOMETRY; RED SHIFT; UNIVERSE; X RADIATION; X-RAY GALAXIES; X-RAY SOURCES

Citation Formats

Hiroi, Kazuo, Ueda, Yoshihiro, Akiyama, Masayuki, and Watson, Mike G., E-mail: hiroi@kusastro.kyoto-u.ac.jp. COMOVING SPACE DENSITY AND OBSCURED FRACTION OF HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI IN THE SUBARU/XMM-NEWTON DEEP SURVEY. United States: N. p., 2012. Web. doi:10.1088/0004-637X/758/1/49.
Hiroi, Kazuo, Ueda, Yoshihiro, Akiyama, Masayuki, & Watson, Mike G., E-mail: hiroi@kusastro.kyoto-u.ac.jp. COMOVING SPACE DENSITY AND OBSCURED FRACTION OF HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI IN THE SUBARU/XMM-NEWTON DEEP SURVEY. United States. https://doi.org/10.1088/0004-637X/758/1/49
Hiroi, Kazuo, Ueda, Yoshihiro, Akiyama, Masayuki, and Watson, Mike G., E-mail: hiroi@kusastro.kyoto-u.ac.jp. 2012. "COMOVING SPACE DENSITY AND OBSCURED FRACTION OF HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI IN THE SUBARU/XMM-NEWTON DEEP SURVEY". United States. https://doi.org/10.1088/0004-637X/758/1/49.
@article{osti_22092082,
title = {COMOVING SPACE DENSITY AND OBSCURED FRACTION OF HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI IN THE SUBARU/XMM-NEWTON DEEP SURVEY},
author = {Hiroi, Kazuo and Ueda, Yoshihiro and Akiyama, Masayuki and Watson, Mike G., E-mail: hiroi@kusastro.kyoto-u.ac.jp},
abstractNote = {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/XMM-Newton Deep Survey 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{sub X} = 10{sup 44-45} erg s{sup -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{sub max} method, we confirm that the comoving space density of luminous AGNs decreases with redshift above z > 3. When combined with the Chandra-COSMOS result of Civano et al., the density decline of AGNs with L{sub X} = 10{sup 44-45} erg s{sup -1} is well represented by a power law of (1 + z){sup -6.2{+-}0.9}. We also determine the fraction of X-ray obscured AGNs with N{sub H} > 10{sup 22} cm{sup -2} in the Compton-thin population to be 0.54{sup +0.17}{sub -0.19}, 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 {+-} 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 {+-} 1.1.},
doi = {10.1088/0004-637X/758/1/49},
url = {https://www.osti.gov/biblio/22092082}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 758,
place = {United States},
year = {Wed Oct 10 00:00:00 EDT 2012},
month = {Wed Oct 10 00:00:00 EDT 2012}
}