scholarly journals Compton-thick active galactic nuclei from the 7 Ms observation in the Chandra Deep Field South

2019 ◽  
Vol 629 ◽  
pp. A133 ◽  
Author(s):  
A. Corral ◽  
I. Georgantopoulos ◽  
A. Akylas ◽  
P. Ranalli
Keyword(s):  
Spectral Analysis ◽  
Data Quality ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Photometric Redshifts ◽  
X Ray ◽  
Spectral Fitting ◽  
Fitting Procedure ◽  
Bayesian Monte Carlo ◽  
X Ray Background

We present the X-ray spectroscopic study of the Compton-thick (CT) active galactic nuclei (AGN) population within the Chandra Deep Field South (CDF-S) by using the deepest X-ray observation to date, the Chandra 7 Ms observation of the CDF-S. We combined an optimized version of our automated selection technique and a Bayesian Monte Carlo Markov chains (MCMC) spectral fitting procedure, to develop a method to pinpoint and then characterize candidate CT AGN as less model dependent and/or data-quality dependent as possible. To obtain reliable automated spectral fits, we only considered the sources detected in the hard (2−8 keV) band from the CDF-S 2 Ms catalog with either spectroscopic or photometric redshifts available for 259 sources. Instead of using our spectral analysis to decide if an AGN is CT, we derived the posterior probability for the column density, and then we used it to assign a probability of a source being CT. We also tested how the model-dependence of the spectral analysis, and the spectral data quality, could affect our results by using simulations. We finally derived the number density of CT AGN by taking into account the probabilities of our sources being CT and the results from the simulations. Our results are in agreement with X-ray background synthesis models, which postulate a moderate fraction (25%) of CT objects among the obscured AGN population.

scholarly journals Compton thick AGN in Chandra sureys

2013 ◽  
Vol 9 (S304) ◽  
pp. 153-154
Author(s):  
Murray Brightman ◽  
Kirpal Nandra
Keyword(s):  
Spectral Analysis ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
High Rate ◽  
Photoelectric Absorption ◽  
X Ray ◽  
Spectral Signatures ◽  
Spectral Fitting ◽  
Spectral Models ◽  
Uniform Sample

AbstractWe present the results from the 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, Compton thick (CT, NH > 104 cm−2) sources. Our sample is comprised of 3088 X-ray selected sources, which has a high rate of redshift completeness (97%). The aim is to produce the largest and cleanest uniform sample of these sources from the data as possible. We identify these sources through X-ray spectral fitting, utilising torus spectral models designed for heavily obscured AGN which self consistently include the spectral signatures of heavy absorption, being Compton scattering, photoelectric absorption and iron Kα fluorescence. We identify a total of 163 CT AGN covering an intrinsic 2-10 keV X-ray luminosity range of 102 −3 × 105 erg s−1 and from z = 0.1-7.

scholarly journals The spectral energy distributions of active galactic nuclei

2019 ◽  
Vol 15 (S341) ◽  
pp. 21-25
Author(s):  
M. J. I. Brown ◽  
K. J. Duncan ◽  
H. Landt ◽  
M. Kirk ◽  
C. Ricci ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Spectral Energy ◽  
Wide Field ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Photometric Redshifts ◽  
X Ray ◽  
Ongoing Work ◽  
Prior Literature

AbstarctWe present ongoing work on the spectral energy distributions (SEDs) of active galactic nuclei (AGNs), derived from X-ray, ultraviolet, optical, infrared and radio photometry and spectroscopy. Our work is motivated by new wide-field imaging surveys that will identify vast numbers of AGNs, and by the need to benchmark AGN SED fitting codes. We have constructed 41 SEDs of individual AGNs and 80 additional SEDs that mimic Seyfert spectra. All of our SEDs span 0.09 to 30μm, while some extend into the X-ray and/or radio. We have tested the utility of the SEDs by using them to generate AGN photometric redshifts, and they outperform SEDs from the prior literature, including reduced redshift errors and flux density residuals.

Active galactic nuclei make the cosmic X-ray background

1993 ◽  
Vol 414 ◽  
pp. L81 ◽  
Author(s):  
Andrzej A. Zdziarski ◽  
Piotr T. Zycki ◽  
Julian H. Krolik
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
X Ray Background

Self-absorbed active galactic nuclei and the cosmic X-ray background

1993 ◽  
Vol 410 ◽  
pp. L7 ◽  
Author(s):  
Piero Madau ◽  
Gabriele Ghisellini ◽  
A. C. Fabian
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
X Ray Background

scholarly journals The X-Ray Background

1992 ◽  
Vol 9 ◽  
pp. 299-308
Author(s):  
Andrzej Soltan
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
Observational Material ◽  
X Ray Background ◽  
Existing Data

AbstractVarious models of the X-ray background are discussed. It is postulated that the only explanation consistent with all the existing data is discrete sources. Present observational material suggests that known classes of active galactic nuclei also dominate the source counts below the lowest detectable flux levels.

scholarly journals Cosmic X-ray Background from Early Active Galactic Nuclei

1990 ◽  
Vol 115 ◽  
pp. 274-275
Author(s):  
Andrzej A. Zdziarski
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
X Ray Background

A model for the origin of the cosmic X-ray background (hereafter XRB) is presented. The component of the background left after subtraction of the known classes of sources is explained by emission from a population of black hole sources at the redshift of z ~ 4-5. The model is presented in more detail elsewhere (Zdziarski 1988). Here, we summarize its most important results.

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