XBOOTESOID ivo://nasa.heasarc/xbootesoid NASA/GSFC HEASARC Brand et al.; Kenter et al. 2026-09-11 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source 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<sub>X</sub>/f<sub>o</sub> > 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<sub>X</sub>/f<sub>o</sub> < 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 . 2006ApJ...641..140B https://heasarc.gsfc.nasa.gov/W3Browse/all/xbootesoid.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=xbootesoid& GET text/xml 180 99999 true 216.27641667 32.30818889 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=xbootesoid GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_xbootesoid&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 Infrared Optical X-ray public xbootesoid XBOOTES: NDWFS Bootes Field Optical & Near IR Counterparts name NDWFS Optical Name meta.id char nullable ra Optical Right Ascension degree pos.eq.ra;meta.main double nullable dec Optical Declination degree pos.eq.dec;meta.main double nullable optical_rank Optical Rank (1=Most Probable in Running Order to Least Probable) short nullable rmag R Magnitude (Vega) mag phot.mag;em.opt.R float nullable imag I Magnitude (Vega) mag phot.mag;em.opt.I float nullable xray_name Designation of the X-Ray Source meta.id;meta.main char nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable num_opt_ctrparts Number of Optical Sources with >1% Probability of Association with X-Ray Source short nullable bw_mag Bw Magnitude (Vega) mag float nullable hardness_ratio X-Ray Hardness Ratio phot.flux;arith.ratio;em.X-ray.medium;em.X-ray.soft float nullable obsid Observation Identifier of X-Ray Pointing meta.id;obs short nullable hb_counts X-Ray Counts (2-7keV Band) short nullable lim_kmag K 50% Completeness Limit mag float nullable fb_counts X-Ray Counts (0.5-7keV Band) short nullable opt_ctrpart_prob Probability of X-Ray Source Having an Optical Counterpart float nullable opt_id_flag Optical Identification Flag short nullable lim_imag I 50% Completeness Limit mag float nullable ra_xray Right Ascension of the X-Ray Source, J2000 char nullable ra_xray_adj Right Ascension of the X-Ray Source, J2000 Shifted to NDWFS Astrometric Frame char nullable hardness_ratio_pos_err X-Ray Hardness Ratio Positive Error stat.error;phot.flux;arith.ratio;em.X-ray.medium;em.X-ray.soft float nullable fb_flux_error X-Ray Flux Error (0.5-7keV Band) erg/s/cm^2 double nullable lim_rmag R 50% Completeness Limit mag float nullable off_set Offset of Optical and X-Ray Positions (arcsec) arcsec float nullable hb_flux_error X-Ray Flux Error (2-7keV Band) erg/s/cm^2 double nullable hb_flux X-Ray Flux (2-7keV Band) erg/s/cm^2 double nullable bayes_match_prob Bayesian Probability of Match float nullable optical_field Optical Field Name char nullable sb_counts X-Ray Counts (0.5-2keV Band) short nullable stellarity Optical Stellarity Parameter float nullable kmag K Magnitude (Vega) mag float nullable sb_flux X-Ray Flux (0.5-2keV Band) erg/s/cm^2 double nullable bii Optical Galactic Latitude degree pos.galactic.lat double nullable lim_bw_mag Bw 50% Completeness Limit mag float nullable hardness_ratio_neg_err X-Ray Hardness Ratio Negative Error stat.error;phot.flux;arith.ratio;em.X-ray.medium;em.X-ray.soft float nullable error_radius X-Ray Positional Error (arcsec) arcsec stat.error;pos float nullable sb_flux_error X-Ray Flux Error (0.5-2keV Band) erg/s/cm^2 double nullable dec_xray_adj Declination of the X-Ray Source, J2000 Shifted to NDWFS Astrometric Frame char nullable fb_flux X-Ray Flux (0.5-7keV Band) erg/s/cm^2 double nullable dec_xray Declination of the X-Ray Source, J2000 char nullable lii Optical Galactic Longitude degree pos.galactic.lon double nullable