Related papers: Constraining Torus Models for AGNs Using X-Ray Obs…
(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…
The nuclear obscurer of Active Galactic Nuclei (AGN) is poorly understood in terms of its origin, geometry and dynamics. We investigate whether physically motivated geometries emerging from hydro-radiative simulations can be differentiated…
We use a sample of 151 local non-blazar AGN selected from the INTEGRAL all-sky hard X-ray survey to investigate if the observed declining trend of the fraction of obscured (i.e. showing X-ray absorption) AGN with increasing luminosity is…
Based on current models of the Cosmic X-ray Background (CXB), heavily obscured Active Galactic Nuclei (AGN) are expected to make up ~10% of the peak emission of the CXB and ~20% of the total population of AGN, yet few of these sources have…
The presence of an obscuring torus around the nucleus of Seyfert galaxies, as supposed in the popular unification scheme, can strongly modify the X--ray spectrum for both type 1 and 2 Seyfert galaxies. We find that if the torus is Compton…
In this work the INTEGRAL hard X-ray selected sample of AGN has been used to investigate the possible contribution of absorbing material distributed within the host galaxies to the total amount of NH measured in the X-ray band. We collected…
Motivated by theoretical expectations that Nuclear Star Clusters (NSCs) in galactic centers may provide a favorable environment for super-massive black holes to form and/or efficiently grow, we set out to measure the fraction of nearby…
We present the systematic broadband X-ray spectral analysis of 52 Compton-thick ($24 \leq \log N_{\mathrm{H}}^{\mathrm{LOS}}/\mathrm{cm}^{-2}$) active galactic nucleus (CTAGN) candidates selected by the Swift/BAT all-sky hard X-ray survey…
The unification theory of active galactic nuclei (AGNs) hypothesizes that all AGNs are surrounded by an anisotropic dust torus and are essentially the same objects but viewed from different angles. However, little is known about the dust…
Highly obscured active galactic nuclei (AGN) are common in nearby galaxies, but are difficult to observe beyond the local Universe, where they are expected to significantly contribute to the black hole accretion rate density. Furthermore,…
We propose a plausible mechanism to explain the formation of the so-called "obscuring tori" around active galactic nuclei (AGNs) based on three-dimensional hydrodynamic simulations including radiative feedback from the central source. The…
We determine the intrinsic shapes and orientations of 27,450 type I and II active galactic nucleus (AGN) galaxies in the spectroscopic sample of the SDSS DR7, by studying the distribution of projected axis ratios of AGN hosts. Our aim is to…
We construct a new sample of 32 obscured active galactic nuclei (AGNs) selected from the Second XMM-Newton Serendipitous Source Catalogue to investigate their multiwavelength properties in relation to the "scattering fraction", the ratio of…
Interferometric measurements in the mid-infrared have shown that the sizes of the warm dust distributions in active galactic nuclei are consistent with their scaling with the square root of their luminosity. We carry out a more detailed…
The torus in Active Galactic Nuclei (AGN) is a complex dynamical structure of gas and dust. It is thought to be composed of an equatorial dusty disk and a polar dusty wind launched by radiation pressure. However, this picture is based on…
A parsec-scale dusty torus is thought to be the cause of Active Galactic Nuclei (AGN) dichotomy in the 1/2 types, narrow/broad emission lines. In a previous work, on the basis of parsec-scale resolution infrared / optical dust maps it was…
Optical observations cannot resolve the structure of active galactic nuclei (AGN), and a unified model for AGN was inferred mostly from indirect methods. Optical reverberation mapping allowed us to constrain the spatial dimension of the…
I present a review of X-ray and mid-IR surveys for Compton-thick Active Galactic Nuclei (AGN). These are the most highly obscured sources having hydrogen column densities >1.5x10^24 cm-2. Key surveys in the local Universe are presented…
We present infrared, optical, and X-ray data of 48 X-ray bright, optically dull AGNs in the COSMOS field. These objects exhibit the X-ray luminosity of an active galactic nucleus (AGN) but lack broad and narrow emission lines in their…
Deep X-ray surveys are providing crucial information on the evolution of AGN and galaxies. We review some of the latest results based on the X-ray spectral analysis of the sources detected in the Chandra Deep Field South, namely: i)…