Related papers: The redshift distribution of the X-ray background

The isotropic diffuse $\gamma$-ray background (IGRB) has been detected by various experiments and recently the Fermi-LAT Collaboration has precisely measured its spectrum in a wide energy range. The origin of the IGRB is still unclear and…

We present an analysis of X-ray variability in a flux limited sample of QSOs. Selected from our deep ROSAT survey, these QSOs span a wide range in redshift ($0.1<z<3.2$) and are typically very faint, so we have developed a method to…

(Abridged) We investigate the far-infrared properties of X-ray sources detected in the Chandra Deep Field-South (CDF-S) survey using the ultra-deep 70um and 24um Spitzer observations taken in this field. We rely on stacking analyses of the…

Gamma-ray bursts (GRBs) are cosmologically distributed, very energetic and very transient sources detected in the gamma-ray domain. The identification of their x-ray and optical afterglows allowed so far the redshift measurement of 150…

The X-ray background (XRB) is due to the aggregate of active galactic nuclei (AGN), which peak in activity at z~1 and is often modeled as the sum of different proportions of unabsorbed, moderately- and heavily-absorbed AGN. We present the…

We explore the role of the group environment in the evolution of AGN at the redshift interval 0.7<z<1.4, by combining deep Chandra observations with extensive optical spectroscopy from the All-wavelength Extended Groth strip International…

One of the key goals in observational cosmology over the next few years will be to establish the redshift distribution of the recently-discovered sub-mm source population. In this brief review I discuss and summarize the redshift…

We are searching for large-scale structures in the distribution of AGN discovered by the ROSAT All-Sky Survey. The RASS detected > 60000 X-ray objects, of which approximately 35% are AGN at z < 0.5. The surface density in the extragalactic…

The origin of the radio synchrotron background (RSB) is currently unknown. Its understanding might have profound implications in fundamental physics or might reveal a new class of radio emitters. In this work, we consider the scenario in…

We summarize our understanding of millisecond radio bursts from an extragalactic population of sources. FRBs occur at an extraordinary rate, thousands per day over the entire sky with radiation energy densities at the source about ten…

We estimate the incidence of multiply-imaged AGNs among the optical counterparts of X-ray selected point-like sources in the XXL field. We also derive the expected statistical properties of this sample, such as the redshift distribution of…

We use the BD2 sample of gamma-ray bursts (GRBs) based on 5.9 years of BATSE DISCLA data with a variety of models of the luminosity function to derive characteristic GRB luminosities, space densities and redshift distributions. Previously…

The deepest extragalactic X-ray observation, the 2 Ms Chandra Deep Field North (CDF-N), resolves ~80% of the total extragalactic cosmic X-ray background (CXB) in the 1-2 keV band. Recent work has shown that 70% of the remaining CXB flux is…

The X-ray column density (NHX) of gamma-ray bursts (GRBs) can probe the local environment of their progenitors over a wide redshift range. Previous work has suggested an increasing trend as a function of redshift. The relevance of the…

Synthesis models of the diffuse Cosmic X-ray Background (CXB) suggest that it can be resolved into discrete sources, primarily Active Galactic Nuclei (AGNs). Measuring the CXB accurately offers a unique probe to study the AGN population in…

The cores of active galactic nuclei (AGN) harbor some of the most extreme conditions of matter and energy in the Universe. One of the major goals of high-energy astrophysics is to probe these extreme environments in the vicinity of…

The usage of cumulative luminosity distributions, constructed thanks to the long-term observations available through wide field hard X-ray imagers, has been recently exploited to study the averaged high energy emission (>17 keV) from…

A soft X-ray excess has been claimed to exist in and around a number of galaxy clusters and this emission has been attributed to the warm-hot intergalactic medium that may constitute most of the baryons in the local universe. We have…

The diffuse extragalactic gamma-ray background (EGRB) above 100 MeV encodes unique information about high-energy processes in the universe. Numerous sources for the EGRB have been proposed, but the two systems which are certain to make some…

We studied the X-ray variability of sources detected in the Chandra Deep Field South (Giacconi et al. 2002), nearly all of which are low to moderate z AGN (Tozzi et al. 2001). We find that 45% of the sources with >100 counts exhibit…