期刊
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
卷 232, 期 1, 页码 -出版社
IOP Publishing Ltd
DOI: 10.3847/1538-4365/aa7847
关键词
catalogs; galaxies: active; galaxies: evolution; surveys; X-rays: galaxies
资金
- National Science Foundation of China (NSFC) [11403021, 11233002, 11421303]
- National Basic Research Program of China (973 program) [2015CB857005, 2015CB857004]
- Fundamental Research Funds for the Central Universities
- Exchange of Researchers program for scientific and technological cooperation between Italy and the People's Republic of China [CN13MO5]
- Strategic Priority Research Program The Emergence of Cosmological Structures of the Chinese Academy of Sciences [XDB09000000]
- CAS Frontier Science Key Research Program [QYZDJ-SSW-SLH006]
- Chinese Top-notch Young Talents Program
- National Thousand Young Talents program
- Ministry of Science and Technology of China [2016YFA0400702]
- Chandra X-ray Center grant [GO4-15130A]
- V.M. Willaman Endowment
- CONICYT-Chile [Basal-CATA PFB-06/2007, FONDECYT Regular 1141218]
- Ministry of Economy, Development, and Tourism's Millennium Science Initiative [IC120009]
- Science and Technology Facilities Council [ST/L00075X/1]
- [NSFC-11473026]
- [NSFC-11673010]
- STFC [ST/L00075X/1, ST/P000541/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/P000541/1, ST/L00075X/1] Funding Source: researchfish
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 powerlaw plus reflection, with possible soft excess and narrow Fe K alpha 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-H, observed fluxes, and absorption-corrected 2-10. keV luminosities L-X for our sample of AGNs, but also identify significant spectral variabilities among them on timescales of years. We find that the N-H 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-H can be well explained by the continuum suppression with increasing N-H. Accounting for the sample incompleteness and bias, we measure the intrinsic distribution of N-H for the CDF-S AGN population and present reselected subsamples that. are complete with respect to N-H. The N-H-complete subsamples enable us to decouple the dependences of N-H on L-X and on redshift. Combining our data with those. from C-COSMOS, we confirm the anticorrelation between the average N-H and L-X 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(obscured) approximate to 0.42 (1 + z)(0.60).
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