XBOOTES:NDWFSBootesFieldOptical&NearIRCounterparts

The XBootes Survey is a 5 ks Chandra survey of the Bootes Field of the NOAO Deep Wide-Field Survey (NDWFS). This survey is unique in that it is the largest (9.3 square degrees) contiguous region imaged in X-ray with complementary deep optical and near-infrared (near-IR) observations. The authors present a catalog of the optical counterparts to the 3213 X-ray point sources detected in the XBootes survey. Using a Bayesian identification scheme, they successfully identified optical counterparts for 98% of the X-ray point sources. The optical colors suggest that the optically detected galaxies are a combination of z < 1 massive early-type galaxies and bluer star-forming galaxies whose optical AGN emission is faint or obscured, whereas the majority of the optically detected point sources are likely quasars over a large redshift range. This large-area, X-ray-bright, optically deep survey enables the authors to select a large subsample of sources (773) with high X-ray to optical flux ratios (f_X/f_o > 10). These objects are likely high-redshift and/or dust-obscured AGNs. These sources have generally harder X-ray spectra than sources with 0.1 < f_X/f_o < 10. Of the 73 X-ray sources with no optical counterpart in the NDWFS catalog, 47 are truly optically blank down to R ~ 25.5 (the average 50% completeness limit of the NDWFS R-band catalogs). These sources are also likely to be high-redshift and/or dust-obscured AGNs. The 9.3 square degrees region of sky chosen to match the area covered with the NDWFS was observed by ACIS-I on the Chandra X-Ray Observatory over a 2 week time interval in 2003 March and April. The data were taken in 126 separate pointings, each observed for ~ 5 ks. The CIAO 3.0.2 wavelet detection algorithm (wavdetect; Freeman et al. 2002) was used to detect X-ray sources in the total (0.5 - 7.0 keV) band data. A probability threshold of 5 x 10-5 was chosen as the best compromise between maximizing the completeness while minimizing the number of spurious detections. The X-ray catalog comprises 3293 unique X-ray sources with >= 4 counts in the total-band images (Paper II). The authors expect only ~ 35 of these sources to be spurious in the full survey (Paper II). For the matching with cataloged optical counterparts, the authors only considered the 3213 X-ray sources that overlap with the NDWFS area. The authors include all multiply matched sources with >1% probability of being the correct optical counterpart. This table contains the X-ray and optical characteristics of the matched optical/X-ray catalog for the Chandra sources in the XBootes and NDWFS survey, and is Version 1.0, dated 21st June 2005. This table was created in November 2006 by the HEASARC based on the file xbootes_cat_xray_opt_IR_21jun_v1.0.txt obtained from the NOAO ftp area <a href="https://www.noao.edu/noao/noaodeep/XBootesPublic/">https://www.noao.edu/noao/noaodeep/XBootesPublic/</a>. This is a service provided by NASA HEASARC .

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