G. L. Granato

Supermassive black hole demography: the match between the local and accreted mass functions

We have performed a detailed analysis of the local supermassive black hole (SMBH) mass function based on both kinematic and photometric data and we have derived an accurate analytical fit in the range 10 6 M BH/M� 5 × 10 9 .W efind a total SMBH mass density of (4.2 ± 1.1) × 10 5 MMpc −3 , about 25 per cent of which is contributed by SMBHs residing in bulges of late-type galaxies. Exploiting up-to-date luminosity functions of hard X-ray and optically selected active galactic nuclei (AGNs), we have studied the accretion history of the SMBH population. If most of the accretion occurs at constant ˙ MBH/MBH ,a s in the case of Eddington-limited accretion and consistent with recent observational estimates, the local SMBH mass function is fully accounted for by mass accreted by X-ray selected AGNs, with bolometric corrections indicated by current observations and a standard mass-to-light conversion efficiency � � 10 per cent. The analysis of the accretion history highlights that the most massive BHs (associated with bright optical quasi-stellar objects) accreted their mass faster and at higher redshifts (typically at z > 1.5), while the lower-mass BHs responsible for most of the hard X-ray background have mostly grown at z < 1.5. The accreted mass function matches the local SMBH mass function if, during the main accretion phases, � � 0.09 (+0.04, −0.03) and the Eddington ratio λ = L/L Edd � 0.3 (+0.3, −0.1) (68 per cent confidence errors). The visibility time, during which AGNs are luminous enough to be detected by the currently available X-ray surveys, ranges from �0.1 Gyr for present-day BH masses M 0 � 10 6 Mto �0.3 Gyr for M 0 10 9 M� . The mass accreted during luminous phases is 25-30 per cent even if we assume extreme values of � (� � 0.3-0.4). An unlikely fine tuning of the parameters would be required to account for the local SMBH mass function accommodating a dominant contribution from dark BH growth (due, for example, to BH coalescence). Ke yw ords: black hole physics - galaxies: active - galaxies: evolution - galaxies: nuclei - cosmology: miscellaneous.

Joint formation of QSOs and spheroids: QSOs as clocks of star formation in spheroids

Direct and indirect observational evidence leads to the conclusion that high-redshift QSOs did shine in the core of early-type protogalaxies during their main episode of star formation. Exploiting this fact, we derive the rate of formation of this kind of stellar system at high redshift by using the QSO luminosity function. The elemental proportions in elliptical galaxies, the descendants of the QSO hosts, suggest that the star formation was more rapid in more massive objects. We show that this is expected to occur in dark matter haloes, when the processes of cooling and heating are considered. This is also confirmed by comparing the observed submm counts with those derived by coupling the formation rate and the star formation rate of the spheroidal galaxies with a detailed model for their SED evolution. In this scenario SCUBA galaxies and Lyman-break galaxies are early-type protogalaxies forming the bulk of their stars before the onset of QSO activity.

Astrophysical and cosmological information from large-scale submillimetre surveys of extragalactic sources

We present a quantitative analysis of the astrophysical and cosmological information that can be extracted from the many important wide-area, shallow surveys that will be carried out in the next few years. Our calculations combine the predictions of the physical model by Granato et al. for the formation and evolution of spheroidal galaxies with up-to-date phenomenological models for the evolution of starburst and normal late-type galaxies and of radio sources. We compute the expected number counts and the redshift distributions of these source populations separately and then focus on protospheroidal galaxies. For the latter objects, we predict the counts and redshift distributions of strongly lensed sources at 250, 350, 500 and 850 μm, the angular correlation function of sources detected in the surveys considered, and the angular power spectra due to clustering of sources below the detection limit in Herschel and Planck surveys. An optimal survey for selecting strongly lensed protospheroidal galaxies is described, and it is shown how they can be easily distinguished from the other source populations. We also discuss the detectability of the imprints of the one-halo and two-halo regimes on angular correlation functions and clustering power spectra, as well as the constraints on cosmological parameters that can be obtained from the determinations of these quantities. The novel data relevant to derive the first submillimetre estimates of the local luminosity functions of starburst and late-type galaxies, and the constraints on the properties of rare source populations, such as blazars, are also briefly described.

Quasar Luminosity Functions from Joint Evolution of Black Holes and Host Galaxies

We show that our previously proposed antihierarchical baryon collapse scenario for the joint evolution of black holes and host galaxies predicts quasar luminosity functions at redshifts 1.5 z 6 and local properties in nice agreement with observations. In our model the quasar activity marks and originates the transition between an earlier phase of violent and heavily dust-enshrouded starburst activity promoting rapid black hole growth, and a later phase of almost passive evolution; the former is traced by the submillimeter-selected sources, while the latter accounts for the high number density of massive galaxies at substantial redshifts z 1.5, the population of extremely red objects, and the properties of local elliptical galaxies.

The Role of the Dust in Primeval Galaxies: A Simple Physical Model for Lyman Break Galaxies and Lyα Emitters

We explore the onset of star formation in the early universe, exploiting the observations of high-redshift LBGs and Lyα emitters (LAEs), in the framework of the galaxy formation scenario elaborated by Granato and coworkers, already successfully tested against the wealth of data on later evolutionary stages. Complementing the model with a simple, physically plausible recipe for the evolution of dust attenuation in metal-poor galaxies, we reproduce the LFs of LBGs and of LAEs at different redshifts. This recipe yields a much faster increase with galactic age of attenuation in more massive galaxies, endowed with higher SFRs. These objects have therefore shorter lifetimes in the LAE and LBG phases and are more easily detected in the dusty submillimeter-bright (SMB) phase. The short UV-bright lifetimes of massive objects strongly mitigate the effect of the fast increase of the massive halo density with decreasing redshift, thus accounting for the weaker evolution of the LBG LF, compared to that of the halo mass function, and the even weaker evolution between z ≈ 6 and z ≈ 3 of the LAE LF. The much lower fraction of LBGs hosting detectable nuclear activity, compared to SMB galaxies, comes out naturally from the evolutionary sequence yielded by the model, which features the coevolution of galaxies and active nuclei. In this framework LAEs are on the average expected to be younger, with lower stellar masses, more compact, and associated with less massive halos than LBGs. Finally, we show that the IGM can be completely reionized at redshift z ≈ 6-7 by massive stars shining in protogalactic spheroids with halo masses from a few times 1010 to a few times 1011 M☉, showing up as faint LBGs with magnitude in the range -17 M1350 -20, without resorting to any special stellar IMF.

The growth of the nuclear black holes in submillimetre galaxies

We show that the ABC scenario we proposed for the co-evolution of spheroids and QSOs predicts accretion rates and masses of supermassive black holes in submillimetre galaxies in keeping with recent X-ray determinations. These masses are well below the local values as well as those predicted by alternative models. The observed column densities may be mostly due to interstellar medium in the galaxy. The contribution of the associated nuclear activity to the X-ray background is likely negligible, while they may contribute a sizeable fraction of ∼10 per cent to hard X-ray cumulative counts at the faintest observed fluxes.

Observational tests of the evolution of spheroidal galaxies

Granato et al(2004) have elaborated a physically grounded model exploiting the mutual feedback between star-forming spheroidal galaxies and the active nuclei growing in their cores to overcome, within the hierarchical clustering scenario for galaxy formation, one of the main challenges facing such scenario, the fact that massive spheroidal galaxies appear to have formed earlier and faster than predicted by previous models. Adopting the choice by Granato et al for the parameters governing the history of the SF,of chemical abundances and of the gas and dust content of galaxies, we are left with only two parameters affecting the time and mass dependent SED of spheroidal galaxies. After complementing the model with a simple description of evolutionary properties of starburst, normal late-type galaxies and AGNs we have successfully compared the model with a broad variety of observational data, deep K-band, ISO, IRAS, SCUBA, radio counts, the corresponding redshift distributions, the IR background spectrum, and also with data for EROs. We also present detailed predictions for the GOODS and SWIRE surveys with the Spitzer Space Telescope. We find that the GOODS deep survey at 24

A highly obscured and strongly clustered galaxy population discovered with the Spitzer Space Telescope

mu

Modeling the spectral energy distribution of ULIRGs I. The radio spectra

m and the SWIRE surveys at 70 and 160

The Star Formation History of the Virgo Early-Type Galaxy NGC 4435: The Spitzer Mid-Infrared View

mu