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Published September 2009 | Published
Journal Article Open

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 deg^2 of the COSMOS field (centered at 10 ^h , +02 ^o ) with an effective exposure of ~160 ks, and an outer 0.4 deg^2 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 deg^2 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.

Additional Information

© 2009 The American Astronomical Society. Received 2008 November 4, accepted for publication 2009. July 29. Published 2009 August 27. We thank the Chandra mission planning team, especially Pat Slane and Jan Vrtilek, and the Chandra pipeline data processing team for the extraordinary efforts they put into the successful scheduling and execution of C-COSMOS. We also thank the rest of COSMOS team whose support has been invaluable in reaching this stage. We thank Bin Luo for sensitivity curves of Chandra Deep Fields. We gratefully thank the Chandra EPO team, in particular Eli Bressert, for creating the true color X-ray image. This research has made use of data obtained from the Chandra Data Archive and software provided by the Chandra X-ray Center (CXC) in the application packages CIAO and Sherpa. This work was supported in part by NASA Chandra grant number GO7-8136A (M.E., C.V., M.B., A.F.), NASA contract NAS8-39073 (Chandra X-ray Center), and by NASA/ADP grant NNX07AT02G (TM at UCSD). In Italy this work is supported by ASI/INAF contracts I/023/05/0, I/024/05/0 and I/088/06, by PRIN/MUR grant 2006-02-5203. In Germany this project is supported by the Bundesministerium für Bildung und Forschung/Deutsches Zentrum für Luft und Raumfahrt and the Max Planck Society.

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