We derive the black hole mass density as a function of redshift from the hard X-ray AGN luminosity function assuming that massive black holes grow via accreting the circumnuclear gases. The derived black hole mass density matches the measured local black hole mass density at z = 0, which requires the average radiative efficiency of AGNs to be ∼ 0.1 − 0.17. The massive black holes in most faint ...

We present a model for the cosmological evolution of quasars (QSOs) under the assumption that they are powered by massive accreting black holes. Accretion flows around massive black holes make a transition from high radiative efficiency (∼ 10%) to low efficiency, advection-dominated flows when Ṁ/ṀEdd falls below the critical rate ∼ 0.3α2 ∼ 10−2 where Ṁ is the mass accretion rate, ṀEdd ∝ M is th...

In this paper, we present a new implementation of feedback due to active galactic nuclei (AGN) in cosmological simulations of galaxy formation. We assume that a fraction of jet energy, which is generated by an AGN, is transferred to the surrounding gas as thermal energy. Combining a theoretical model of mass accretion onto black holes with a multiphase description of star-forming gas, we self-c...

We study the accretion flows from the circumbinary disks onto the supermassive binary black holes in a subparsec scale of the galactic center , using a smoothed particles hydrodynamics (SPH) code. Simulation models are presented in four cases of a circular binary with equal masses and unequal masses, and of an eccentric binary with equal masses and unequal masses. We find that the circumblack-h...