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  1. OA@INAF
  2. PRODOTTI RICERCA INAF
  3. 1 CONTRIBUTI IN RIVISTE (Journal articles)
  4. 1.01 Articoli in rivista
Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12386/26693
Title: X-Ray Spectral Analyses of AGNs from the 7Ms Chandra Deep Field-South Survey: The Distribution, Variability, and Evolutions of AGN Obscuration
Authors: Liu, Teng
TOZZI, Paolo 
Wang, Jun-Xian
Brandt, William N.
VIGNALI, CRISTIAN
Xue, Yongquan
Schneider, Donald P.
COMASTRI, Andrea 
Yang, Guang
Bauer, Franz E.
Paolillo, Maurizio 
Luo, Bin
GILLI, Roberto 
Wang, Q. Daniel
Giavalisco, Mauro
Ji, Zhiyuan
Alexander, David M.
MAINIERI, VINCENZO
Shemmer, Ohad
Koekemoer, Anton
RISALITI, Guido
Issue Date: 2017
Journal: THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 
Number: 232
Issue: 1
First Page: 8
Abstract: We present a detailed spectral analysis of the brightest active galactic nuclei (AGNs) identified in the 7Ms Chandra Deep Field-South (CDF-S) survey over a time span of 16 years. Using a model of an intrinsically absorbed power-law plus reflection, with possible soft excess and narrow Fe Kα line, we perform a systematic X-ray spectral analysis, both on the total 7Ms exposure and in four different periods with lengths of 2-21 months. With this approach, we not only present the power-law slopes, column densities {N}<SUB>{{H</SUB>}}, observed fluxes, and absorption-corrected 2-10 keV luminosities L <SUB> X </SUB> for our sample of AGNs, but also identify significant spectral variabilities among them on timescales of years. We find that the {N}<SUB>{{H</SUB>}} variabilities can be ascribed to two different types of mechanisms, either flux-driven or flux-independent. We also find that the correlation between the narrow Fe line EW and {N}<SUB>{{H</SUB>}} can be well explained by the continuum suppression with increasing {N}<SUB>{{H</SUB>}}. Accounting for the sample incompleteness and bias, we measure the intrinsic distribution of {N}<SUB>{{H</SUB>}} for the CDF-S AGN population and present reselected subsamples that are complete with respect to {N}<SUB>{{H</SUB>}}. The {N}<SUB>{{H</SUB>}}-complete subsamples enable us to decouple the dependences of {N}<SUB>{{H</SUB>}} on L <SUB> X </SUB> and on redshift. Combining our data with those from C-COSMOS, we confirm the anticorrelation between the average {N}<SUB>{{H</SUB>}} and L <SUB> X </SUB> of AGN, and find a significant increase of the AGN-obscured fraction with redshift at any luminosity. The obscured fraction can be described as {f}<SUB>obscured</SUB>}≈ 0.42 {(1+z)} 0.60
URI: http://hdl.handle.net/20.500.12386/26693
URL: https://arxiv.org/abs/1703.00657
https://iopscience.iop.org/article/10.3847/1538-4365/aa7847
ISSN: 0067-0049
DOI: 10.3847/1538-4365/aa7847
Bibcode ADS: 2017ApJS..232....8L
Fulltext: open
Appears in Collections:1.01 Articoli in rivista

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1703.00657.pdfVersione su arXiv1.14 MBAdobe PDFView/Open
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