A simple model for the evolution of supermassive black holes and the quasar population

Abstract

An empirically motivated model is presented for accretion-dominated growth of supermassive black holes (SMBH) in galaxies, and the implications are studied for the evolution of the quasar population in the Universe. We investigate the core aspects of the quasar population, including space density evolution, evolution of the characteristic luminosity, plausible minimum masses of quasars, the mass function of SMBH and their formation epoch distribution. Our model suggests that the characteristic luminosity in the quasar luminosity function arises primarily as a consequence of a characteristic mass scale above which there is a systematic separation between the black hole and the halo merging rates. At lower mass scales, black hole merging closely tracks the merging of dark haloes. When combined with a declining efficiency of black hole formation with redshift, the model can reproduce the quasar luminosity function over a wide range of redshifts. The observed space density evolution of quasars is well described by formation rates of SMBH above ∼10 8 M . The inferred mass density of SMBH agrees with that found independently from estimates of the SMBH mass function derived empirically from the quasar luminosity function.

On the Faint End of the High‐Redshift Active Galactic Nucleus Luminosity Function

“…We first discuss the Wyithe & Loeb (2003; see also Mahmood et al 2005) model which connects the SMBH and DM halo masses as M / M 5/3 halo (1 þ z) 5/2 , derived from a basic AGN feedbackconstrained model. We shall refer to this model as model A in the rest of the paper.…”

“…In this section we discuss possible physical implications for SMBH evolution from our estimated AGN LF. We compute the total AGN LF from the formation rates of DM halos simply as (e.g., Mahmood et al 2005)…”

The Coevolution of Supermassive Black Holes and Massive Galaxies at High Redshift

“…The model envisages that such a finding is due to a selection bias. In fact, the high luminosity tail (L AGN 10 47 erg s −1 ) of the luminosity function of optically selected AGNs/QSOs at high redshift z 3 comprises objects, that are on the high side ( 3 σ) of the local Γ distribution (e.g., Wyithe & Loeb 2003;Mahmood et al 2005;Lapi et al 2006, see their Fig. 4; Lauer et al 2007).…”

“…This conclusion is quite reasonable, since α res embodies a large number of physical mechanisms and astrophysical settings, as we shall discuss in § 5.2. Actually this scatter is essential to reproduce the QSO luminosity functions at very high redshift (z 4), that sample only 3 σ objects (Wyithe & Loeb 2003;Mahmood et al 2005;Lapi et al 2006;Fanidakis et al 2012). All in all, the final mass of the BH itself can be approximated as (see Fig.…”

Astrophysics in 2005

“…This year, Jin et al (2005) favor them for dwarf spheroidal galaxies because they promote shallow (core vs. cusp) central density profiles. If, however, they contribute a typical density of only 1.5 # Mpc Ϫ3 (Mahmood et al 2005, on evolutionary sce-5 10 M , narios vs. data), then they are not even a 1% solution, however respectable they may be. And we proceed onward to Fermi balls (Munyaneza & Biermann 2005); baryon clumps (Froggatt & Nielson 2005); neutralino clumps of about one Earth mass and one AU in size (Diemand et al 2005), one of which should pass through the solar system every 3000 yr. 15 Annihilation in galactic ones could be the unidentified gamma ray sources.…”