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Description
The COSMOS-Legacy survey is a 4.6Ms Chandra program that has imaged 2.2deg^2^ of the COSMOS field with an effective exposure of ~160ks over the central 1.5deg^2^ and of ~80ks in the remaining area. The survey is the combination of 56 new observations obtained as an X-ray Visionary Project with the previous C-COSMOS survey. We describe the reduction and analysis of the new observations and the properties of 2273 point sources detected above a spurious probability of 2x10^-5^. We also present the updated properties of the C-COSMOS sources detected in the new data. The whole survey includes 4016 point sources (3814, 2920 and 2440 in the full, soft, and hard band). The limiting depths are 2.2x10^-16^, 1.5x10^-15^, and 8.9x10^-16^erg/cm^2^/s in the 0.5-2, 2-10, and 0.5-10keV bands, respectively. The observed fraction of obscured active galactic nuclei with a column density >10^22^/cm^2^ from the hardness ratio (HR) is ~50^+17^_-16_%. Given the large sample we compute source number counts in the hard and soft bands, significantly reducing the uncertainties of 5%-10%. For the first time we compute number counts for obscured (HR>-0.2) and unobscured (HR<-0.2) sources and find significant differences between the two populations in the soft band. Due to the unprecedent large exposure, COSMOS-Legacy area is three times larger than surveys at similar depths and its depth is three times fainter than surveys covering similar areas. The area-flux region occupied by COSMOS-Legacy is likely to remain unsurpassed for years to come.
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