MARCHESI, STEFANOSTEFANOMARCHESILANZUISI, GiorgioGiorgioLANZUISICivano, F.F.CivanoIwasawa, K.K.IwasawaSuh, H.H.SuhCOMASTRI, AndreaAndreaCOMASTRIZamorani, G.G.ZamoraniAllevato, V.V.AllevatoGriffiths, R.R.GriffithsMiyaji, T.T.MiyajiRanalli, P.P.RanalliSalvato, M.M.SalvatoSchawinski, K.K.SchawinskiSilverman, J.J.SilvermanTreister, E.E.TreisterUrry, C. M.C. M.UrryVignali, C.C.Vignali2020-07-062020-07-0620160004-637Xhttp://hdl.handle.net/20.500.12386/26350We 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 {N}<SUB>{{H</SUB>},{{z}}} 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 {N}<SUB>{{H</SUB>},{{z}}} ∼ 3 times higher than type 1 AGNs. We find that ∼15% of type 1 AGNs have {N}<SUB>{{H</SUB>},{{z}}}\gt {10}<SUP>22</SUP> cm<SUP>-2</SUP>, I.e., are obscured according to the X-ray spectral fitting; the vast majority of these sources have {L}<SUB>2{--</SUB>10{keV}} \gt 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 {N}<SUB>{{H</SUB>},{{z}}}\lt {10}<SUP>22</SUP> cm<SUP>-2</SUP>, and most of these sources have low X-ray luminosities (L {}<SUB>2{--</SUB>10{keV}} \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 {N}<SUB>{{H</SUB>},{{z}}} and host-galaxy mass and star formation rate, although part of this trend is due to a redshift selection effect.STAMPAenArticle10.3847/0004-637X/830/2/1002-s2.0-84994029475000386488200003https://iopscience.iop.org/article/10.3847/0004-637X/830/2/1002016ApJ...830..100MFIS/05 - ASTRONOMIA E ASTROFISICA