| Preprint typeset using LATEX style emulateapj v. 04/21/05 THE CHANDRA XBOÖTES SURVEY- III: OPTICAL AND NEAR-IR COUNTERPARTS (2009) | |||||||||||||
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| The XBoötes Survey is a 5-ks Chandra survey of the Boötes Field of the NOAO Deep Wide-Field Survey (NDWFS). This survey is unique in that it is the largest (9.3 deg2), contiguous region imaged in X-ray with complementary deep optical and near-IR observations. We present a catalog of the optical counterparts to the 3,213 X-ray point sources detected in the XBoötes survey. Using a Bayesian identification scheme, we 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. Our large area, X-ray bright, optically deep survey enables us to select a large sub-sample of sources (773) with high X-ray to optical flux ratios (fx/fo 10). These objects are likely high redshift and/or dust obscured AGN. These sources have generally harder X-ray spectra than sources with 0.1 fx/fo 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 AGN. Subject headings: X-ray Survey, AGN, Cosmology 1. | |||||||||||||
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