Abstract
We present the most up-to-date X-ray luminosity function (XLF) and absorption function of Active Galactic Nuclei (AGNs) over the redshift range from 0 to 5, utilizing the largest, highly complete sample ever available obtained from surveys performed with Swift/BAT, MAXI, ASCA, XMM-Newton, Chandra, and ROSAT. The combined sample, including that of the Subaru/XMM-Newton Deep Survey, consists of 4039 detections in the soft (0.5--2 keV) and/or hard ($>2$ keV) band. We utilize a maximum likelihood method to reproduce the count-rate versus redshift distribution for each survey, by taking into account the evolution of the absorbed fraction, the contribution from Compton-thick (CTK) AGNs, and broad band spectra of AGNs including reflection components from tori based on the luminosity and redshift dependent unified scheme. We find that the shape of the XLF at $z \sim 1-3$ is significantly different from that in the local universe, for which the luminosity dependent density evolution model gives much better description than the luminosity and density evolution model. These results establish the standard population synthesis model of the X-Ray Background (XRB), which well reproduces the source counts, the observed fractions of CTK AGNs, and the spectrum of the hard XRB. The number ratio of CTK AGNs to the absorbed Compton-thin (CTN) AGNs is constrained to be $\approx$0.5--1.6 to produce the 20--50 keV XRB intensity within present uncertainties, by assuming that they follow the same evolution as CTN AGNs. The growth history of supermassive black holes is discussed based on the new AGN bolometric luminosity function.
Highlights
Understanding the cosmological evolution of supermassive black holes (SMBHs) is a key issue in modern astrophysics
We present our latest results of AGN X-ray luminosity function (XLF) over the redshift range from 0 to 5, by utilizing one of the largest combined samples ever available, obtained from surveys of various depths, widths, and energy bands performed with Swift/BAT, the Monitor of All-sky X-ray Image (MAXI; Matsuoka et al 2009), ASCA, XMM-Newton, Chandra, and ROSAT
In a normal maximum likelihood (ML) fit performed to a completely independent data set, the 1σ error for a single parameter is defined as the deviation from the best fit when the L-value is increased by Δ − L = 1.0 from its minimum value
Summary
Understanding the cosmological evolution of supermassive black holes (SMBHs) is a key issue in modern astrophysics. The good correlation of the mass of an SMBH in a galactic center with that of the bulge in the present-day universe (e.g., Magorrian et al 1998; Ferrarese & Merritt 2000; Gebhardt et al 2000; Marconi & Hunt 2003; Haring & Rix 2004; Hopkins et al 2007; Kormendy & Bender 2009; Gultekin et al 2009) indicates that SMBHs and galaxies co-evolved in the past. This idea is supported by the similarity of the global history between star formation and SMBH growth (Marconi et al 2004). The surface number density of the faintest X-ray AGNs reaches ∼104 deg−2 (Xue et al 2011)
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