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

K. Nobuta, M. Akiyama, Y. Ueda, M. G. Watson, J. Silverman, K. Hiroi, K. Ohta, F. Iwamuro, K. Yabe, N. Tamura, Y. Moritani, M. Sumiyoshi, N. Takato, M. Kimura, T. Maihara, G. Dalton, I. Lewis, D. Bonfield, H. Lee, E. Curtis-LakeE. MacAulay, F. Clarke, K. Sekiguchi, C. Simpson, S. Croom, M. Ouchi, H. Hanami, T. Yamada

研究成果: Article査読

44 被引用数 (Scopus)

抄録

In order to investigate the growth of supermassive black holes (SMBHs), we construct the black hole mass function (BHMF) and Eddington ratio distribution function (ERDF) of X-ray-selected broad-line active galactic nuclei (AGNs) at z ∼ 1.4 in the Subaru XMM-Newton Deep Survey (SXDS) field. A significant part of the accretion growth of SMBHs is thought to take place in this redshift range. Black hole masses of X-ray-selected broad-line AGNs are estimated using the width of the broad Mg II line and 3000 Å monochromatic luminosity. We supplement the Mg II FWHM values with the Hα FWHM obtained from our NIR spectroscopic survey. Using the black hole masses of broad-line AGNs at redshifts between 1.18 and 1.68, the binned broad-line AGN BHMFs and ERDFs are calculated using the V maxmethod. To properly account for selection effects that impact the binned estimates, we derive the corrected broad-line AGN BHMFs and ERDFs by applying the maximum likelihood method, assuming that the ERDF is constant regardless of the black hole mass. We do not correct for the non-negligible uncertainties in virial BH mass estimates. If we compare the corrected broad-line AGN BHMF with that in the local universe, then the corrected BHMF at z = 1.4 has a higher number density above 108 Mbut a lower number density below that mass range. The evolution may be indicative of a downsizing trend of accretion activity among the SMBH population. The evolution of broad-line AGN ERDFs from z = 1.4 to 0 indicates that the fraction of broad-line AGNs with accretion rates close to the Eddington limit is higher at higher redshifts.

本文言語English
論文番号143
ジャーナルAstrophysical Journal
761
2
DOI
出版ステータスPublished - 2012 12月 10

ASJC Scopus subject areas

  • 天文学と天体物理学
  • 宇宙惑星科学

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