scholarly journals The X-Ray Background from Star-Forming Galaxies

1990 ◽  
Vol 139 ◽  
pp. 412-413
Author(s):  
Richard E. Griffiths
Keyword(s):  
Energy Range ◽  
Active Galactic Nuclei ◽  
Surface Density ◽  
Galactic Nuclei ◽  
X Ray ◽  
Star Forming ◽  
Smooth Component ◽  
Spatial Fluctuations ◽  
Deep Survey ◽  
X Ray Background

It has been established observationally that at least 30% of the all-sky X-ray background (XRB) in the energy range of 1–3 keV comes from active galactic nuclei (AGN) in the redshift interval of 0.4 to 1.2 (Griffiths et al. 1983, 1988); it is also quite plausible that AGN contribute half of the XRB in the 1–3 keV range (Morisawa and Takahara 1989). However, analysis of spatial fluctuations in the Einstein deep survey counts (Hamilton and Helfand 1987; Barcons and Fabian 1989) has indicated the presence of a relatively smooth component of the XRB with a corresponding surface density of discrete sources of at least several thousand per square degree.

The Fall of Active Galactic Nuclei and the Rise of Star-forming Galaxies: A Close Look at the Chandra Deep Field X-Ray Number Counts

2004 ◽  
Vol 128 (5) ◽  
pp. 2048-2065 ◽  
Author(s):  
F. E. Bauer ◽  
D. M. Alexander ◽  
W. N. Brandt ◽  
D. P. Schneider ◽  
E. Treister ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
Star Forming ◽  
Number Counts

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

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.

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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