期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 428, 期 1, 页码 354-369出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/sts034
关键词
methods: data analysis; techniques: imaging spectroscopy; surveys; galaxies: active; galaxies: high-redshift; X-rays: galaxies
资金
- agreement ASI-INAF [I/009/10/0]
- PRIN-INAF
- CXC [SP1-12007A]
- NASA ADP [NNX10AC99G]
- USTC [ZC9850290195]
- Basal-CATA [PFB-06/2007]
- CONICYT-Chile [FONDECYT 1101024]
- Chandra X-ray Center [SAO SP1-12007B]
- STFC [ST/I001573/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/I001573/1] Funding Source: researchfish
- ICREA Funding Source: Custom
We present results from a spectral analysis of a sample of high-redshift (z > 3) X-ray-selected active galactic nucleus (AGN) in the 4-Ms Chandra Deep Field-South (CDF-S), the deepest X-ray survey to date. The sample is selected using the most recent spectroscopic and photometric information available in this field. It consists of 34 sources with median redshift z = 3.7, 80 median net counts in the 0.5-7 keV band and median rest-frame absorption-corrected luminosity L2-10 keV approximate to 1.5 x 10(44) erg s(-1). Spectral analysis for the full sample is presented and the intrinsic column density distribution, corrected for observational biases using spectral simulations, is compared with the expectations of X-ray background (XRB) synthesis models. We find that approximate to 57 per cent of the sources are highly obscured (N-H > 10(23) cm(-2)). Source number counts in the 0.5-2 keV band down to flux F0.5-2 keV approximate to 4 x 10(-17) erg s(-1) cm(-2) are also presented. Our results are consistent with a decline of the AGN space density at z > 3 and suggest that, at those redshifts, the AGN obscured fraction is in agreement with the expectations of XRB synthesis models.
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