MARCHESI, STEFANOSTEFANOMARCHESICivano, F.F.CivanoElvis, M.M.ElvisSalvato, M.M.SalvatoBrusa, M.M.BrusaCOMASTRI, AndreaAndreaCOMASTRIGILLI, RobertoRobertoGILLIHasinger, G.G.HasingerLANZUISI, GiorgioGiorgioLANZUISIMiyaji, T.T.MiyajiTreister, E.E.TreisterUrry, C. M.C. M.UrryVignali, C.C.VignaliZamorani, G.G.ZamoraniAllevato, V.V.AllevatoCappelluti, N.N.CappellutiCardamone, C.C.CardamoneFinoguenov, A.A.FinoguenovGriffiths, R. E.R. E.GriffithsKarim, A.A.KarimLaigle, C.C.LaigleLaMassa, S. M.S. M.LaMassaJahnke, K.K.JahnkeRanalli, P.P.RanalliSchawinski, K.K.SchawinskiSchinnerer, E.E.SchinnererSilverman, J. D.J. D.SilvermanSmolcic, V.V.SmolcicSuh, H.H.SuhTrakhtenbrot, B.B.Trakhtenbrot2020-07-022020-07-0220160004-637Xhttp://hdl.handle.net/20.500.12386/26289We present the catalog of optical and infrared counterparts of the Chandra COSMOS-Legacy Survey, a 4.6 Ms Chandra program on the 2.2 deg<SUP>2</SUP> of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the I, K, and 3.6 μm identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS, using new K and 3.6 μm information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while ≃54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is available online. We study several X-ray to optical (X/O) properties: with our large statistics we put better constraints on the X/O flux ratio locus, finding a shift toward faint optical magnitudes in both soft and hard X-ray band. We confirm the existence of a correlation between X/O and the the 2-10 keV luminosity for Type 2 sources. We extend to low luminosities the analysis of the correlation between the fraction of obscured AGNs and the hard band luminosity, finding a different behavior between the optically and X-ray classified obscured fraction.STAMPAenArticle10.3847/0004-637X/817/1/342-s2.0-84955482893000368872400034https://iopscience.iop.org/article/10.3847/0004-637X/817/1/342016ApJ...817...34MFIS/05 - ASTRONOMIA E ASTROFISICA