The Chandra Cosmos Survey. I. Overview and Point Source Catalog

The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.5 deg2 of the COSMOS field (centered at 10h, +02o) with an effective exposure of ∼160 ks, and an outer 0.4 deg2 area with an effective exposure of ∼80 ks. The limiting source detection depths are 1.9 × 10−16 erg cm−2 s−1 in the soft (0.5–2 keV) band, 7.3 × 10−16 erg cm−2 s−1 in the hard (2–10 keV) band, and 5.7 × 10−16 erg cm−2 s−1 in the full (0.5–10 keV) band. Here we describe the strategy, design, and execution of the C-COSMOS survey, and present the catalog of 1761 point sources detected at a probability of being spurious of <2 × 10−5 (1655 in the full, 1340 in the soft, and 1017 in the hard bands). By using a grid of 36 heavily (∼50%) overlapping pointing positions with the ACIS-I imager, a remarkably uniform (±12%) exposure across the inner 0.5 deg2 field was obtained, leading to a sharply defined lower flux limit. The widely different point-spread functions obtained in each exposure at each point in the field required a novel source detection method, because of the overlapping tiling strategy, which is described in a companion paper. This method produced reliable sources down to a 7–12 counts, as verified by the resulting logN–logS curve, with subarcsecond positions, enabling optical and infrared identifications of virtually all sources, as reported in a second companion paper. The full catalog is described here in detail and is available online.