A. Lamastra

Faint high-redshift AGN in the Chandra deep field south: the evolution of the AGN luminosity function and black hole demography

Context. We present detection and analysis of faint X-ray sources in the Chandra deep field south (CDFS) using the 4 Ms Chandra observation. Aims. We place constraints on active galactic nuclei (AGN) luminosity functions at z = 3–7, its cosmological evolution, and highredshift black hole and AGN demography. Methods. We use a new detection algorithm, using the entire three-dimensional data-cube (position and energy), and searching for X-ray counts at the position of high-z galaxies in the GOODS-South survey. Results. This optimized technique results in the identification of 54 AGN at z > 3, 29 of which are new detections. Applying stringent completeness criteria, we derive AGN luminosity functions in the redshift bins 3–4, 4–5, and >5.8 and for 42.75 3( 18 +17 −10 %). Their optical counterparts do not show any reddening and we thus conclude that the size of the X-ray absorber is likely smaller than the dust sublimation radius. We finally report the discovery of a highly star-forming galaxy at z = 3.47, arguing that its X-ray luminosity is likely dominated by stellar sources. If confirmed, this would be one of the farthest objects in which stellar sources have been detected in X-rays.

The MBH-M* relation for X-ray-obscured, red QSOs at 1.2 < z < 2.6

We present near-infrared spectra, obtained with SINFONI and XShooter observations at ESO VLT, of nine dusty, red QSOs at 1.2 10^{21} - 10^{22} cm^{-2}) and show a broad Ha component in the NIR spectra. We complement this sample with twelve additional sources taken from the literature with similar properties resulting in a total sample of 21 X-ray obscured, intermediate type (1.8-1.9), dusty reddened QSOs. From the broad Ha line we have computed the BH masses through the virial formula and derived Eddington ratios. Moreover, from optical/IR multi-component SED fitting we have derived the stellar mass of their host galaxies and their SFRs. We find that most of the sources in our sample are hosted in starburst and main sequence star-forming galaxies with Eddington ratios lambda>0.1. We find a strong trend with the BH mass i.e. less massive objects are scattered below and above the local relation while the most massive ones are mainly located above it. We also studied the evolution of these sources on the M_BH-M_star plane compared to a sample of optically blue type--1 QSOs and we find that obscured red QSOs show a ratio of M_BH to M_star that increases with redshift which is consistent with or slightly lower than what has been found for blue QSOs. These sources may represent the blow-out phase at the end of the rapid BH growth and immediately preceding the classical blue QSOs typically sampled in optical surveys. They in fact show evidence of outflows in the ionized gas component, but their BH has already fully formed.

AGN wind scaling relations and the co-evolution of black holes and galaxies

This work was supported by ASI/INAF contract I/009/10/0 and INAF PRIN 2011, 2012 and 2014. MB acknowledges support from the FP7 Career Integration Grant “eEASy” (CIG 321913). LZ acknowledges support from ASI/INAF grant I/037/12/0. CF acknowledges funding from the European Union Horizon 2020 research and innovation programme under the Marie SklodowskaCurie grant agreement No 664931. CC acknowledges funding from the European Union Horizon 2020 research and innovation programme under the Marie SklodowskaCurie grant agreement No 664931 and support from Swiss National Science Foundation Grants PP00P2 138979 and PP00P2 166159. RM acknowledges the ERC Advanced Grant 695671 QUENCH and support from the Science and Technology Facilities Council (STFC).

Galaxy Formation in Warm Dark Matter Cosmology

We investigate for the first time the effects of a Warm Dark Matter (WDM) power spectrum on the statistical properties of galaxies using a semi-analytic model of galaxy formation. The WDM spectrum we adopt as a reference case is suppressed - compared to the standard Cold Dark Matter (CDM) case - below a cut-off scale ~ 1 Mpc corresponding (for thermal relic WDM particles) to a mass m_X=0.75 keV. This ensures consistency with present bounds provided by the microwave background WMAP data and by the comparison of hydrodynamical N-body simulations with observed Lyman-{\alpha} forest. We run our fiducial semi-analytic model with such a WDM spectrum to derive galaxy luminosity functions (in B, UV, and K bands) and the stellar mass distributions over a wide range of cosmic epochs, to compare with recent observations and with the results in the CDM case. The predicted color distribution of galaxies in the WDM model is also checked against the data. When compared with the standard CDM case, the luminosity and stellar mass distributions we obtain assuming a WDM spectrum are characterized by: i) a flattening of the faint end slope and ii) a sharpening of the cutoff at the bright end for z \lesssim 0.8. We discuss how the former result is directly related to the smaller number of low-mass haloes collapsing in the WDM scenario, while the latter is related to the smaller number of satellite galaxies accumulating in massive haloes at low redshift, thus suppressing the accretion of small lumps on the central, massive galaxies. These results shows how a adopting a WDM power spectrum may contribute to solve two major problems of CDM galaxy formation scenarios, namely, the excess of predicted faint (low mass) galaxies at low and - most of all - high redshifts, and the excess of bright (massive) galaxies at low redshifts.

Triggering Active Galactic Nuclei in Hierarchical Galaxy Formation: Disk instability vs. Interactions

Using a semi analytic model for galaxy formation we investigate the effects of Black Hole accretion triggered by disk instabilities (DI) in isolated galaxies on the evolution of AGN. Specifically, we took on, developed and expanded the Hopkins & Quataert (2011) model for the mass inflow following disk perturbations, and compare the corresponding evolution of the AGN population with that arising in a scenario where galaxy interactions trigger AGN (IT mode). We extended and developed the DI model by including different disk surface density profiles, to study the maximal contribution of DI to the evolution of the AGN population. We obtained the following results: i) for luminosities corresponding to

The interaction-driven starburst contribution to the cosmic star formation rate density

M_{1450}\gtrsim -26

A model for the X-ray absorption in Compton-thin AGN

the DI mode can provide the BH accretion needed to match the observed AGN luminosity functions up to

Probing AGN triggering mechanisms through the starburstiness of the host galaxies

z \approx 4.5

Tracing outflows in the AGN forbidden region with SINFONI

; in such a luminosity range and redshift, it can compete with the IT scenario as the main driver of cosmological evolution of AGN; ii) The DI scenario cannot provide the observed abundance of high-luminosity QSO with

Galaxy Formation in WDM Cosmology

M_{1450}\lesssim -26