Related papers: The X-ray Background and AGNs

The growth of supermassive black holes across cosmic time leaves a radiative imprint recorded in the X-ray background (XRB). The XRB spectral shape suggests that a large population of distant, hidden nuclei must exist, which are now being…

Merging the Chandra and XMM-Newton deep surveys with the previously identified ROSAT sample, almost 1000 AGN-1 covering five orders of magnitude in 0.5-2 keV flux limit and six orders of magnitude in survey solid angle were identified with…

(abridged)The majority of Active Galactic Nuclei (AGN) suffer from significant obscuration by surrounding dust and gas. X-ray surveys in the 2-10 keV band will miss the most heavily-obscured AGN in which the absorbing column density exceeds…

We combine a semi-analytic galaxy formation model (Nulsen and Fabian 1997) with a prescription for the obscured growth of massive black holes (Nulsen and Fabian 2000; Fabian 1999), to reproduce the hard X-ray background (XRB), the local…

The cosmic X-ray background (CXB), which peaks at an energy of ~30 keV, is produced primarily by emission from accreting supermassive black holes (SMBHs). The CXB therefore serves as a constraint on the integrated SMBH growth in the…

While it is understood that the origin of the Cosmic X-ray Background (CXRB) can be explained in terms of a combination of obscured and unobscured AGN, the identity of these obscured AGN showing up in large numbers at faint fluxes remains…

Hard X-ray selection is the most efficient way to discriminate between accretion-powered sources, such as AGN, from sources dominated by starlight. Hard X-rays are also less affected than other bands by obscuration. We have then carried out…

Models for the origin of the hard X-ray background have suggested that sources with the most accretion activity lie hidden in highly obscured AGN. We report on our study of hard, serendipitous sources in the fields of Chandra clusters with…

XMM-Newton spectra of five red, 2MASS AGN, selected from a sample observed by Chandra to be relatively X-ray bright and to cover a range of hardness ratios, confirm the presence of substantial absorbing material in three sources with…

A synthesis model for the cosmic X-ray Background (XRB) is presented, which includes a proper treatment of Compton scattering in the absorbing matter for type 2 AGN. Evidence for a decrease of the relative importance of type 2 AGN at high…

In this paper we combine archival and proprietary XMM-Newton observations (about 5deg^2) that overlap with the Sloan Digital Sky Survey to explore the nature of the moderate-z X-ray population. We focus on X-ray sources with optically red…

We report on an optical (SDSS) and X-ray (XMM) study of an optically selected sample of four dual AGN systems at projected separations of 30--60~kpc. All sources are detected in the X-ray band (0.3-10 keV); seven objects are optically…

Most of the soft and a growing fraction of the harder X-ray background has been resolved into emission from point sources, yet the resolved fraction above 7 keV has only been poorly constrained. We use ~700 ks of XMM-Newton observations of…

Using 100ks of XMM-Newton data on the Lockman Hole, we show how the X-ray background 'spectral paradox' is being resolved. We find the summed spectra of the Type I AGN, Type II AGN, and the unidentified objects. We conclude that the hard…

We report the final optical identifications of the medium-depth (~60 ksec), contiguous (2 deg^2) XMM-Newton survey of the COSMOS field. XMM-Newton has detected ~800 X-ray sources down to limiting fluxes of ~5x10^{-16}, ~3x10^{-15}, and…

The emission from individual X-ray sources in the Chandra Deep Fields and XMM-Newton Lockman Hole shows that almost half of the hard X-ray background above 6 keV is unresolved and implies the existence of a missing population of heavily…

The origin of the hard X-ray background (XRB) as a superposition of unabsorbed and absorbed Active Galactic Nuclei is now widely accepted as the standard model. The identification of faint X-ray sources in ROSAT, ASCA, and BeppoSAX…

With recent Chandra observations, at least 60% of the 2-10 keV background is now resolved into discrete sources. Here we present deep optical, NIR, submm, and 20 cm (radio) images, as well as high-quality optical spectra, of a complete…

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…

We present a synthesis model of the X-ray background based on the cross-correlation between mid-infrared and X-ray surveys, where the distribution of type 2 sources is assumed to follow that of luminous infrared galaxies while type 1…