The Chandra Cosmos Legacy Survey: Overview and Point Source Catalog

Abstract

The COSMOS-Legacy survey is a 4.6 Ms Chandra program that has imaged 2.2 deg2 of the COSMOS field with an effective exposure of <?MML &simeq; 160 ks over the central 1.5 deg2 and of <?MML &simeq; 80 ks 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 2 × 10−5. 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 2.2 × 10−16, 1.5 × 10−15, and 8.9 × 10−16 <?MML erg cm &minus; 2 s &minus; 1 in the 0.5–2, 2–10, and 0.5–10 keV bands, respectively. The observed fraction of obscured active galactic nuclei with a column density &gt;1022 cm−2 from the hardness ratio (HR) is ∼50 <?MML &minus; 16 &plus; 17 %. 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 &gt; −0.2) and unobscured (HR &lt; −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.

The NuSTAR Extragalactic Surveys: X-Ray Spectroscopic Analysis of the Bright Hard-band Selected Sample

“…Objects from the deep fields all have unique counterparts at lower energies from either the Chandra (Lehmer et al 2005;Xue et al 2011;Civano et al 2012Civano et al , 2016Goulding et al 2012) or XMM-Newton (Brusa et al 2010;Ranalli et al 2013) surveys of these same fields, with the exception of one source in the ECDF-S field (ecdfs5; this source has two possible counterparts, one at low and one at high redshift; see Table 2 and Appendix).…”

“…This can be currently done: (i) locally (z 0.1 < ) by targeting bright sources (e.g., 5 1 0 erg s cm »´-) with hard X-ray ( 10 > keV) surveys, such as those performed by Swift/BAT and INTEGRAL Ajello et al 2008); and (ii) at high redshifts (z 1 > ) with the most sensitive Chandra/XMMNewton observations of the deep/medium survey fields (e.g., Civano et al 2016;Luo et al 2017). Through either spectral or hardness ratio analysis, they allow one to quantify and characterize the obscured Compton-thin ( N log cm…”

X-rays across the galaxy population – II. The distribution of AGN accretion rates as a function of stellar mass and redshift

“…We match the NIR-selected catalogues with X-ray detected sources in the Chandra imaging of our fields (Alexander et al 2003;Xue et al 2011;Nandra et al 2015;Civano et al 2016), where all the Chandra data have been reprocessed using our own procedures (see Laird et al 2009;Georgakakis et al 2014;Nandra et al 2015;Aird et al 2015). We also extract X-ray data (total counts, background counts, and effective exposures) at the positions of the remaining NIR-selected sources that are not matched to a significant X-ray detection, We extract counts within a circular aperture that corresponds to a 70 per cent enclosed energy fraction for the exposure-weighted Chandra point spread function at each source position.…”

A 16 deg2 survey of emission-line galaxies at z &lt; 1.5 in HSC-SSP Public Data Release 1

“…We use the 4.6 Ms X-ray data by the Chandra COSMOSLegacy Survey (Civano et al 2016) which almost fully covers the UD-COSMOS field. The D-COSMOS field is partially covered.…”