TY - JOUR
T1 - THE CHANDRA COSMOS-LEGACY SURVEY
T2 - SOURCE X-RAY SPECTRAL PROPERTIES
AU - Marchesi, S.
AU - Lanzuisi, G.
AU - Civano, F.
AU - Iwasawa, K.
AU - Suh, H.
AU - Comastri, A.
AU - Zamorani, G.
AU - Allevato, V.
AU - Griffiths, R.
AU - Miyaji, T.
AU - Ranalli, P.
AU - Salvato, M.
AU - Schawinski, K.
AU - Silverman, J.
AU - Treister, E.
AU - Urry, C. M.
AU - Vignali, C.
PY - 2016/10/20
Y1 - 2016/10/20
N2 - 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.
AB - 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.
KW - galaxies: active
KW - galaxies: nuclei
KW - X-rays: galaxies
UR - http://www.scopus.com/inward/record.url?scp=84994029475&partnerID=8YFLogxK
U2 - 10.3847/0004-637X/830/2/100
DO - 10.3847/0004-637X/830/2/100
M3 - Article
AN - SCOPUS:84994029475
SN - 0004-637X
VL - 830
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 100
ER -