The Chandra Deep Field-South Survey: 2 Ms Source Catalogs

Abstract

We present point-source catalogs for the ≈2 Ms exposure of the Chandra Deep Field-South (CDF-S); this is one of the two most sensitive X-ray surveys ever performed. The survey covers an area of ≈436 arcmin^2 and reaches on-axis sensitivity limits of ≈1.9 × 10^(−17) and ≈1.3 × 10^(−16) ergs cm^(−2) s^(−1) for the 0.5-2.0 and 2-8 keV bands, respectively. Four hundred and sixty-two X-ray point sources are detected in at least one of three X-ray bands that were searched; 135 of these sources are new compared to the previous ≈1 Ms CDF-S detections. Source positions are determined using centroid and matched-filter techniques; the median positional uncertainty is ≈0.36''. The X-ray-to-optical flux ratios of the newly detected sources indicate a variety of source types; ≈55% of them appear to be active galactic nuclei, while ≈45% appear to be starburst and normal galaxies. In addition to the main Chandra catalog, we provide a supplementary catalog of 86 X-ray sources in the ≈2 Ms CDF-S footprint that was created by merging the ≈250 ks Extended Chandra Deep Field-South with the CDF-S; this approach provides additional sensitivity in the outer portions of the CDF-S. A second supplementary catalog that contains 30 X-ray sources was constructed by matching lower significance X-ray sources to bright optical counterparts (R < 23.8); the majority of these sources appear to be starburst and normal galaxies. The total number of sources in the main and supplementary catalogs is 578. Optical R-band counterparts and basic optical and infrared photometry are provided for the X-ray sources in the main and supplementary catalogs. We also include existing spectroscopic redshifts for 224 of the X-ray sources. The average backgrounds in the 0.5-2.0 and 2-8 keV bands are 0.066 and 0.167 counts Ms^(−1) pixel^(−1), respectively, and the background counts follow Poisson distributions. The effective exposure times and sensitivity limits of the CDF-S are now comparable to those of the ≈2 Ms Chandra Deep Field-North (CDF-N). We also present cumulative number counts for the main catalog and compare the results to those for the CDF-N. The soft-band number counts for these two fields agree well with each other at fluxes higher than ≈2 × 10^(−16) ergs cm^(−2) s^(−1), while the CDF-S number counts are up to ≈25% smaller than those for the CDF-N at fluxes below ≈2 × 10^(−16) ergs cm^(−2) s^(−1) in the soft band and ≈2 × 10^(−15) ergs cm^(−2) s^(−1) in the hard band, suggesting small field-to-field variations.

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