Related papers: The evolution of obscured accretion
Context: X-ray surveys of Active Galactic Nuclei (AGN) indicate `cosmic downsizing', with the comoving number density of high-luminosity objects peaking at higher redshifts (z about 2) than low-luminosity AGN (z<1). Aims: We test whether…
The physical and evolutionary relation between growing supermassive black holes (AGN) and host galaxies is currently the subject of intense research activity. Nevertheless, a deep theoretical understanding of such a relation is hampered by…
The cosmological evolution of Active Galactic Nuclei (AGN) is important for understanding the mechanism of accretion onto supermassive black holes, and the related evolution of the host galaxy. In this work, we include objects with very low…
We present a comprehensive synthesis model for the AGN evolution and the growth of supermassive black holes in the Universe. We solve the continuity equation for SMBH mass function using the locally determined one as a boundary condition,…
Extragalactic X-ray surveys are exceptionally powerful tools for studying the evolution of supermassive black holes and their host galaxies, by detecting large numbers of active galactic nuclei (AGN) and star-forming galaxies over a wide…
The Great Observatories Origins Deep Survey (GOODS) combines deep HST and Spitzer imaging with the deepest Chandra/XMM observations to probe obscured AGN at higher redshifts than previous multiwavelength surveys. We present a…
The high angular resolution and sensitivity of the Chandra X-ray Observatory has yielded large numbers of faint X-ray sources with measured redshifts in the soft (0.5-2 keV) and hard (2-8 keV) energy bands. Many of these sources show few…
Obscured AGN are fundamental to understand the history of Super Massive Black Hole growth and their influence on galaxy formation. However, the Compton-thick AGN (NH>1e24 cm^-2) population is basically unconstrained, with less than few…
The Cosmic X-ray background carries the information of cosmic accretion onto super-massive black holes. The intensity at its peak can be used to constrain the integrated space density of highly obscured AGNs. Determining the shape and…
In order to test active galactic nucleus (AGN) unification and evolutionary models, we measured the AGN clustering properties as a function of AGN obscuration defined in terms of hydrogen column density, $N_{\rm H}$. In addition to…
The growth of supermassive black holes (SMBH) through accretion is accompanied by the release of enormous amounts of energy which can either be radiated away, as happens in quasars, advected into the black hole, or disposed of in kinetic…
The discoveries made over the past 20 years by Chandra and XMM-Newton surveys in conjunction with multiwavelength imaging and spectroscopic data available in the same fields have significantly changed the view of the supermassive black hole…
The fraction of AGN with photoelectric absorption in the X-rays ranging from NH of 10^{22} up to about 10^{24} cm^{-2} (Compton-thin) appears observationally to be anticorrelated to their luminosity Lx. This recently found evidence is used…
Hard X-ray observations are the most efficient way to discriminate accretion-powered sources from star-light. Furthermore, hard X-rays are less affected than other bands by obscuration. For these reasons the advent of imaging instruments…
As a result of deep hard X-ray observations by Chandra and XMM-Newton a significant fraction of the cosmic X-ray background (CXRB) has been resolved into individual sources. These objects are almost all active galactic nuclei (AGN) and…
Active Galactic Nuclei (AGN) are powered by the accretion of material onto a supermassive black hole (SMBH), and are among the most luminous objects in the Universe. However, the huge radiative power of most AGN cannot be seen directly, as…
We report the discovery of a Compton-thick Active Galactic Nucleus (AGN) at z=4.76 in the 4 Ms Chandra Deep Field South. This object was selected as a V-band dropout in HST/ACS images and previously recognized as an AGN from optical…
We combine optical and X-ray data for eight low redshift ($z\sim 0.06$) poor groups of galaxies from the {\it XI}({\it XMM/IMACS}) Groups Project to study the AGN population in the group environment. Among $\sim 140$ group members, we…
We present the results from an X-ray spectral analysis of active galactic nuclei (AGN) in the Chandra Deep Field-South, AEGIS-XD and Chandra-COSMOS surveys, focussing on the identification and characterisation of the most heavily obscured,…
We review results from cosmic X-ray surveys of active galactic nuclei (AGNs) over the past ~ 15 yr that have dramatically improved our understanding of growing supermassive black holes in the distant universe. First, we discuss the utility…