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

Abstract

We present the most up-to-date X-ray luminosity function (XLF) and absorption\nfunction of Active Galactic Nuclei (AGNs) over the redshift range from 0 to 5,\nutilizing the largest, highly complete sample ever available obtained from\nsurveys performed with Swift/BAT, MAXI, ASCA, XMM-Newton, Chandra, and ROSAT.\nThe combined sample, including that of the Subaru/XMM-Newton Deep Survey,\nconsists of 4039 detections in the soft (0.5--2 keV) and/or hard ($>2$ keV)\nband. We utilize a maximum likelihood method to reproduce the count-rate versus\nredshift distribution for each survey, by taking into account the evolution of\nthe absorbed fraction, the contribution from Compton-thick (CTK) AGNs, and\nbroad band spectra of AGNs including reflection components from tori based on\nthe luminosity and redshift dependent unified scheme. We find that the shape of\nthe XLF at $z \\sim 1-3$ is significantly different from that in the local\nuniverse, for which the luminosity dependent density evolution model gives much\nbetter description than the luminosity and density evolution model. These\nresults establish the standard population synthesis model of the X-Ray\nBackground (XRB), which well reproduces the source counts, the observed\nfractions of CTK AGNs, and the spectrum of the hard XRB. The number ratio of\nCTK AGNs to the absorbed Compton-thin (CTN) AGNs is constrained to be\n$\\approx$0.5--1.6 to produce the 20--50 keV XRB intensity within present\nuncertainties, by assuming that they follow the same evolution as CTN AGNs. The\ngrowth history of supermassive black holes is discussed based on the new AGN\nbolometric luminosity function.\n