Local Black Hole Mass Function Research Articles

Local supermassive black holes and relics of active galactic nuclei

We quantify the importance of mass accretion during AGN phases in the growth of supermassive black holes (BH) by comparing the mass function of black holes in the local universe with that expected from AGN relics, which are black holes grown entirely with mass accretion during AGN phases. The local BH mass function (BHMF) is estimated by applying the well-known correlations between BH mass, bulge luminosity and stellar velocity dispersion to galaxy luminosity and velocity functions. The density of BHs in the local universe is .To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Local supermassive black holes, relics of active galactic nuclei and the X-ray background

We quantify the importance of mass accretion during AGN phases in the growth of supermassive black holes (BH) by comparing the mass function of black holes in the local universe with that expected from AGN relics, which are black holes grown entirely with mass accretion during AGN phases. The local BH mass function (BHMF) is estimated by applying the well-known correlations between BH mass, bulge luminosity and stellar velocity dispersion to galaxy luminosity and velocity functions. The density of BH's in the local universe is 4.6 (-1.4; +1.9) (h/0.7)^2 10^5 Msun Mpc^-3. The relic BHMF is derived from the continuity equation with the only assumption that AGN activity is due to accretion onto massive BH's and that merging is not important. We find that the relic BHMF at z=0 is generated mainly at z 10^9 Msun. (abridged)

Constraints on QSO Models from a Relation between the QSO Luminosity Function and the Local Black Hole Mass Function

QSOs are believed to be powered by accretion onto massive black holes (BHs). In this paper, assuming that each central BH in nearby galaxies has experienced the QSO phase and ignoring BH mergers, we establish a relation between the QSO luminosity function (LF) and the local BH mass function (MF). The QSOLF is jointly controlled by the luminosity evolution of individual QSOs and the triggering history of the accretion onto seed BHs. By comparing the time integral of the QSOLF with that inferred from local BHs, we separate the effect of the luminosity evolution of individual QSOs from the effect of the triggering history. Assuming that the nuclear luminosity evolution includes two phases (first increasing at the Eddington luminosity with growth of BHs and then declining), we find that observations are generally consistent with the expected relation between the QSOLF and the local BHMF and obtain the following constraints on QSO models and BH growth: (i) The QSO mass-to-energy efficiency should be ≳0.1. (ii) The lifetime (defined directly through the luminosity evolution of individual QSOs here) should be ≳4 × 107 yr. The characteristic declining timescale in the second phase should be significantly shorter than the Salpeter timescale τSp, and BH growth should not be dominated by the second phase. (iii) The ratio of obscured QSOs/AGNs to optically bright QSOs should be not larger than 7 at MB ~ -23 and 3 at MB ~ -26 if = 0.31, and not larger than 1 at MB ~ -23 and negligible at MB ~ -26 if = 0.1. (iv) It is unlikely that most QSOs are accreting at super-Eddington luminosities. We point out that it is hard to accurately estimate the value of the QSO lifetime from the QSOLF and/or the local BHMF, if it is longer than a certain value (e.g., ~4τSp in this study). We discuss the importance of accurate measurements of the intrinsic scatter in the BH mass and velocity dispersion relation of local galaxies and the scatter in the bolometric correction of QSOs. We also discuss some possible applications of the work in this paper, such as to the study of the demography of QSOs and the demography of normal galaxies at intermediate redshift.

Self‐regulated Growth of Supermassive Black Holes in Galaxies as the Origin of the Optical and X‐Ray Luminosity Functions of Quasars

We postulate that supermassive black holes grow in the centers of galaxies until they unbind the galactic gas that feeds them. We show that the corresponding self-regulation condition yields a correlation between black hole mass (Mbh) and galaxy velocity dispersion (σ) as inferred in the local universe and recovers the observed optical and X-ray luminosity functions of quasars at redshifts up to z ~ 6 based on the hierarchical evolution of galaxy halos in a Λ-dominated cold dark matter cosmology. With only one free parameter and a simple algorithm, our model yields the observed evolution in the number density of optically bright or X-ray-faint quasars with 2 z 6 across 3 orders of magnitude in bolometric luminosity and 3 orders of magnitude in comoving density per logarithm of luminosity. The self-regulation condition identifies the dynamical time of galactic disks during the epoch of peak quasar activity (z ~ 2.5) as the origin of the inferred characteristic quasar lifetime of ~107 yr. Since the lifetime becomes comparable to the Salpeter e-folding time at this epoch, the model also implies that the Mbh-σ relation is a product of feedback-regulated accretion during the peak of quasar activity. The mass density in black holes accreted by that time is consistent with the local black hole mass density ρbh ~ (2.3) × 105 M☉ Mpc-3, which we have computed by combining the Mbh-σ relation with the measured velocity dispersion function of Sloan Digital Sky Survey galaxies. Comparison of the local black hole mass function with that inferred from combining the feedback relation with the halo mass function suggests that most massive (>109 M☉) black holes may have already been in place by z ~ 6. Applying a similar self-regulation principle to supernova-driven winds from starbursts, we find that the local ratio between the black hole mass and the stellar mass of galactic spheroids should be ~0.001, independent of mass and in agreement with observations. This ratio increases with redshift, although the Mbh-σ relation is redshift-independent.

Fundamental galaxy parameters for radio-loud active galactic nuclei and the black hole-radio power connection

We have determined the central velocity dispersions and surface brightness profiles for a sample of powerful radio galaxies in the redshift range 0.06 < z < 0.31, which were selected on the basis of their young radio source. The optical hosts follow the fundamental plane of elliptical galaxies, showing that young radio sources reside in normal ellipticals, as do other types of radio galaxies into which these objects are believed to evolve. As young radio sources are relatively straightforward to select and the contributions of the active galactic nuclei (AGN) light to the optical spectra are minimal, these objects can readily be used to study the evolution of the fundamental plane of elliptical galaxies out to z = 1, independent of optical selection effects. The black hole masses, M b h , of the objects in our sample have been determined using the tight empirical relation of M b h with central velocity dispersion, σ e , and for literature samples of classical radio galaxies and optically selected ellipticals. Only the optically selected inactive galaxies are found to exhibit a correlation between M b h and radio luminosity. In contrast, the radio powers of the AGN in the samples do not correlate with M b h at all, with objects at a given black hole mass ranging over seven orders of magnitude in radio power. It is unlikely that beaming of the radio emission is responsible for the range in radio powers. We have been able to tie in the local population of powerful radio sources with its parent population of inactive elliptical galaxies: the local black hole mass function has been determined using the elliptical galaxy luminosity function and the Faber-Jackson and M b h -σ relations. This was combined with the fraction of radio-loud black holes as a function of M b h , as determined from the optically selected galaxy sample, to derive the local volume-density of radio galaxies and the distribution of their black hole masses. These are shown to be consistent with the local radio luminosity function and the distribution of black hole masses as found in the radio-selected samples, and confirms that elliptical galaxies comprise the large majority of the radio-loud population of active galaxies.

Observational constraints on growth of massive black holes

We study the observational constraints on the growth of massive black holes (BHs) in galactic nuclei. We use the velocity dispersions of early-type galaxies obtained by the SDSS and the relation between BH mass and velocity dispersion to estimate the local BH mass density to be 2.5x10^5 Msun/Mpc^3. We also use the QSO luminosity function from the 2dF Redshift Survey to estimate the BH mass density accreted during optically bright QSO phases. The local BH mass density is consistent with the density accreted during optically bright QSO phases if QSOs have an efficiency 0.1. By studying the continuity equation for the BH mass distribution, including the effect of BH mergers, we find relations between the local BH mass function and the QSO luminosity function. If the BH mass is assumed to be conserved during BH mergers, comparison of the predicted relations with the observations suggests that luminous QSOs (L_{bol}>10^{46} erg/s) have a high efficiency (e.g. 0.2), and the growth of high-mass BHs (>10^8 Msun) comes mainly from accretion during optically bright QSO phases, or that luminous QSOs have a super-Eddington luminosity. If luminous QSOs are not accreting with super-Eddington luminosities and the growth of low-mass BHs also occurs mainly during optically bright QSO phases, less luminous QSOs must accrete with a low efficiency 0.1.

Hawking radiation and back-reaction in a unitary theory of 2D quantum gravity

We construct a manifestly unitary quantum theory of the CGHS model of 2D dilaton gravity by performing a reduced phase space quantization. It is shown that physical states exist such that in the semiclassical limit the Hawking radiation is present. A new method for calculating the back-reaction corrections to the classical metric is introduced, based on the expansion of the metric operator in a power series of the matter energy-momentum tensor operator. The first order correction to a local black hole mass function is evaluated, and it agrees with the expected semiclassical behaviour. We briefly discuss the calculation of higher-order corrections and implications for the quantum fate of a 2D black hole.