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 Î and of the intrinsic absorption based on the sources' optical classification: type 1 AGNs have a slightly steeper mean photon index Î than type 2 AGNs, which, on the other hand, have average times higher than type 1 AGNs. We find that â¼15% 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.
Titolo: | THE CHANDRA COSMOS-LEGACY SURVEY: SOURCE X-RAY SPECTRAL PROPERTIES | |
Autori: | ||
Data di pubblicazione: | 2016 | |
Rivista: | ||
Digital Object Identifier (DOI): | http://dx.doi.org/10.3847/0004-637X/830/2/100 | |
Parole Chiave: | galaxies: active; galaxies: nuclei; X-rays: galaxies; Astronomy and Astrophysics; Space and Planetary Science | |
Handle: | http://hdl.handle.net/11384/72350 | |
Appare nelle tipologie: | 1.1 Articolo in rivista |