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THE CHANDRA COSMOS-LEGACY SURVEY : SOURCE X-RAY SPECTRAL PROPERTIES

Marchesi, S.; Lanzuisi, G.; Civano, F.; Iwasawa, K.; Suh, H.; Comastri, A.; Zamorani, G.; Allevato, V.; Griffiths, R. and Miyaji, T., et al. (2016) In Astrophysical Journal 830(2).
Abstract

We present the X-ray spectral analysis of the 1855 extragalactic sources in the Chandra COSMOS-Legacy survey catalog having more than 30 net counts in the 0.5-7 keV band. A total of 38% of the sources are optically classified type 1 active galactic nuclei (AGNs), 60% are type 2 AGNs, and 2% are passive, low-redshift galaxies. We study the distribution of AGN photon index Γ and of the intrinsic absorption based on the sources' optical classification: type 1 AGNs have a slightly steeper mean photon index Γ than type 2 AGNs, which, on the other hand, have average times higher than type 1 AGNs. We find that ∼15% of type 1 AGNs have cm-2, i.e., are obscured according to the X-ray spectral fitting; the vast majority of these... (More)

We present the X-ray spectral analysis of the 1855 extragalactic sources in the Chandra COSMOS-Legacy survey catalog having more than 30 net counts in the 0.5-7 keV band. A total of 38% of the sources are optically classified type 1 active galactic nuclei (AGNs), 60% are type 2 AGNs, and 2% are passive, low-redshift galaxies. We study the distribution of AGN photon index Γ and of the intrinsic absorption based on the sources' optical classification: type 1 AGNs have a slightly steeper mean photon index Γ than type 2 AGNs, which, on the other hand, have average times higher than type 1 AGNs. We find that ∼15% of type 1 AGNs have cm-2, i.e., are obscured according to the X-ray spectral fitting; the vast majority of these sources have 1044 erg s-1. The existence of these objects suggests that optical and X-ray obscuration can be caused by different phenomena, the X-ray obscuration being, for example, caused by dust-free material surrounding the inner part of the nuclei. Approximately 18% of type 2 AGNs have cm-2, and most of these sources have low X-ray luminosities (L2-10keV < 1043 erg s-1). We expect a part of these sources to be low-accretion, unobscured AGNs lacking broad emission lines. Finally, we also find a direct proportional trend between and host-galaxy mass and star formation rate, although part of this trend is due to a redshift selection effect.

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keywords
galaxies: active, galaxies: nuclei, X-rays: galaxies
in
Astrophysical Journal
volume
830
issue
2
publisher
University of Chicago Press
external identifiers
  • scopus:84994029475
  • wos:000386488200003
ISSN
0004-637X
DOI
10.3847/0004-637X/830/2/100
language
English
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yes
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4f47a18e-dbe9-4c9d-8291-985fe7b303ce
date added to LUP
2016-11-21 13:31:55
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2017-11-05 05:09:43
@article{4f47a18e-dbe9-4c9d-8291-985fe7b303ce,
  abstract     = {<p>We present the X-ray spectral analysis of the 1855 extragalactic sources in the Chandra COSMOS-Legacy survey catalog having more than 30 net counts in the 0.5-7 keV band. A total of 38% of the sources are optically classified type 1 active galactic nuclei (AGNs), 60% are type 2 AGNs, and 2% are passive, low-redshift galaxies. We study the distribution of AGN photon index Γ and of the intrinsic absorption based on the sources' optical classification: type 1 AGNs have a slightly steeper mean photon index Γ than type 2 AGNs, which, on the other hand, have average times higher than type 1 AGNs. We find that ∼15% of type 1 AGNs have cm<sup>-2</sup>, i.e., are obscured according to the X-ray spectral fitting; the vast majority of these sources have 10<sup>44</sup> erg s<sup>-1</sup>. The existence of these objects suggests that optical and X-ray obscuration can be caused by different phenomena, the X-ray obscuration being, for example, caused by dust-free material surrounding the inner part of the nuclei. Approximately 18% of type 2 AGNs have cm<sup>-2</sup>, and most of these sources have low X-ray luminosities (L<sub>2-10keV</sub> &lt; 10<sup>43</sup> erg s<sup>-1</sup>). We expect a part of these sources to be low-accretion, unobscured AGNs lacking broad emission lines. Finally, we also find a direct proportional trend between and host-galaxy mass and star formation rate, although part of this trend is due to a redshift selection effect.</p>},
  articleno    = {100},
  author       = {Marchesi, S. and Lanzuisi, G. and Civano, F. and Iwasawa, K. and Suh, H. and Comastri, A. and Zamorani, G. and Allevato, V. and Griffiths, R. and Miyaji, T. and Ranalli, P. and Salvato, M. and Schawinski, K. and Silverman, J. and Treister, E. and Urry, C. M. and Vignali, C.},
  issn         = {0004-637X},
  keyword      = {galaxies: active,galaxies: nuclei,X-rays: galaxies},
  language     = {eng},
  month        = {10},
  number       = {2},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {THE CHANDRA COSMOS-LEGACY SURVEY : SOURCE X-RAY SPECTRAL PROPERTIES},
  url          = {http://dx.doi.org/10.3847/0004-637X/830/2/100},
  volume       = {830},
  year         = {2016},
}