Related papers: Identifying Compton-thick AGNs with Machine learni…

Compton-thick active galactic nuclei (CT-AGNs), characterized by a significant absorption with column densities of $\mathrm{N_H}\geqslant 1.5\times 10^{24} \ \mathrm{cm}^{-2}$, emit feeble X-ray radiation and are even undetectable by X-ray…

Compton-thick active galactic nuclei (CT-AGNs), defined by column density $\mathrm{N_H} \geqslant 1.5 \times 10^{24} \ \mathrm{cm}^{-2}$, are so heavily absorbed that their X-ray emission is often feeble, even undetectable by X-ray…

We present the X-ray spectroscopic study of the Compton-thick (CT) active galactic nuclei (AGN) population within the $\textit{Chandra}$ Deep Field South (CDF-S) by using the deepest X-ray observation to date, the $\textit{Chandra}$ 7 Ms…

Even in deep X-ray surveys, Compton-thick active galactic nuclei (CT AGNs, ${\rm N_H} \geqslant 1.5~\times~10^{24}~{\rm cm}^{-2}$) are difficult to be identified due to X-ray flux suppression and their complex spectral shape. However, the…

Using a suite of X-ray, mid-IR and optical active galactic nuclei (AGN) luminosity indicators, we search for Compton-thick (CT) AGNs with intrinsic L_X>10^42erg/s at z~0.03-0.2, a region of parameter space which is currently poorly…

We present new estimates on the fraction of heavily X-ray obscured, Compton-thick (CT) active galactic nuclei (AGNs) out to a redshift of $z \leq$ 0.8. From a sample of 540 AGNs selected by mid-IR (MIR) properties in observed X-ray survey…

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 constrain the number density and evolution of Compton-thick Active Galactic Nuclei (AGN), and their contribution to the extragalactic X-ray background. In the local Universe we use the wide area surveys from the Swift and INTEGRAL…

Compton Thick (CT) AGN are a key ingredient of Cosmic X-ray Background (CXB) synthesis models, but are still an elusive component of the AGN population beyond the local Universe. Multi-wavelength surveys are the only way to find them at z >…

(abridged) We identify a numerically significant population of heavily obscured AGNs at z~0.5-1 in the Chandra Deep Field-South (CDF-S) and Extended Chandra Deep Field-South by selecting 242 X-ray undetected objects with infrared-based star…

We present a new method to predict the line-of-sight column density (NH) values of active galactic nuclei (AGN) based on mid-infrared (MIR), soft, and hard X-ray data. We developed a multiple linear regression machine learning algorithm…

We analyze observations obtained with the Chandra X-ray Observatory of bright Compton thick active galactic nuclei (AGNs), those with column densities in excess of 1.5 x 10^{24} cm^{-2} along the lines of sight. We therefore view the…

We estimate the abundance of Compton-thick (CT) active galactic nuclei (AGN) based on our joint model of X-ray and infrared backgrounds. At L_{rest 2-10 keV} > 10^42 erg/s, the CT AGN density predicted by our model is a few 10^-4 Mpc^-3…

Heavily obscured accretion is believed to represent an important stage in the growth of supermassive black holes, and to play an important role in shaping the observed spectrum of the Cosmic X-ray Background (CXB). Hard X-ray (E$>$10 keV)…

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 analyse Compton-thick active galactic nuclei (CT AGNs), a heavily obscured subclass that challenges traditional X-ray diagnostics. Using 243 sources from the 70-Month \textit{SWIFT}/BAT catalogue (26 CT, 217 non-CT), we investigate their…

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…

To fully understand cosmic black hole growth we need to constrain the population of heavily obscured active galactic nuclei (AGN) at the peak of cosmic black hole growth ($z\sim$1-3). Sources with obscuring column densities higher than…

We present a selection technique to detect Compton-thick (CT) active galactic nuclei (AGNs) in the 3XMM/SDSS-DR7 cross-correlation. A subsample of 3481 X-ray sources that are detected in the hard band (2-8 keV) and have photometric…

Heavily obscured, Compton Thick (CT, NH>10^24 cm^-2) AGN may represent an important phase in AGN/galaxy co-evolution and are expected to provide a significant contribution to the cosmic X-ray background (CXB). Through direct X-ray spectra…