BLACK HOLE MASS AND EDDINGTON RATIO DISTRIBUTION FUNCTIONS OF X-RAY-SELECTED BROAD-LINE AGNs AT<i>z</i>∼ 1.4 IN THE SUBARU<i>XMM-NEWTON</i>DEEP FIELD

Abstract

In order to investigate the growth of super-massive black holes (SMBHs), we\nconstruct the black hole mass function (BHMF) and Eddington ratio distribution\nfunction (ERDF) of X-ray-selected broad-line AGNs at z~1.4 in the Subaru\nXMM-Newton Deep Survey field. In this redshift range, a significant part of the\naccretion growth of SMBHs is thought to be taking place. Black hole masses of\nX-ray-selected broad-line AGNs are estimated using the width of the broad MgII\nline and the 3000A monochromatic luminosity. We supplement the MgII FWHM values\nwith the Ha FWHM obtained from our NIR spectroscopic survey. Using the black\nhole masses of broad-line AGNs at redshifts between 1.18 and 1.68, the binned\nbroad-line AGN BHMF and ERDF are calculated using the Vmax method. To properly\naccount for selection effects that impact the binned estimates, we derive the\ncorrected broad-line AGN BHMF and ERDF by applying the Maximum Likelihood\nmethod, assuming that the ERDF is constant regardless of the black hole mass.\nWe do not correct for the non-negligible uncertainties in virial BH mass\nestimates. If we compare the corrected broad-line AGN BHMF with that in the\nlocal Universe, the corrected BHMF at z~1.4 has a higher number density above\n10^8 Msolar but a lower number density below that mass range. The evolution may\nbe indicative of a down-sizing trend of accretion activity among the SMBH\npopulation. The evolution of broad-line AGN ERDF from z=1.4 to 0 indicates that\nthe fraction of broad-line AGNs with accretion rate close to the\nEddington-limit is higher at higher redshifts.\n