CANDELS H-Band Selected Chandra Source Catalog CANDELSCXO ivo://nasa.heasarc/candelscxo NASA/GSFC HEASARC Cappelluti et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source Improving the capabilities of detecting faint X-ray sources is fundamental to increase the statistics on faint high-z AGN and star-forming galaxies. The authors performed a simultaneous maximum likelihood point-spread function (PSF) fit in the 0.5-2 keV and 2-7 keV energy bands of the 4 Ms Chandra Deep Field South (CDFS) data at the position of the 34,930 CANDELS H-band selected galaxies. For each detected source, they provide X-ray photometry and optical counterpart validation. The authors validated this technique by means of a ray-tracing simulation, and detected a total of 698 X-ray point-sources with a likelihood L > 4.98 (i.e.> 2.7sigma). They show that the prior knowledge of a deep sample of Optical-NIR galaxies leads to a significant increase of the detection of faint (i.e. ~ 10<sup>-17</sup> erg s<sup>-1</sup> cm<sup>-2</sup> in the 0.5-2 keV band) sources with respect to "blind" X-ray detections. By including previous catalogs, this work increases the total number of X-ray sources detected in the 4 Ms CDFS, CANDELS area to 793, which represents the largest sample of extremely faint X-ray sources assembled to date. These results suggest that a large fraction of the optical counterparts of our X-ray sources determined by likelihood ratio actually coincides with the priors used for the source detection. Most of the newly detected sources are likely star-forming galaxies or faint absorbed AGN. The authors identified a few sources with putative photometric redshift z > 4. Despite the low number statistics, this sample significantly increases the number of X-ray selected candidate high-z AGN. The 4-Ms CDFS consists of 23 observations described in Table 1 of Luo et al. (2008, ApJS, 179, 19) plus 31 other pointings described in Xue et al. (2011, ApJS, 195, 10, hereafter X11) for a total exposure of ~4 Ms. For the purpose of this paper, the authors employed only observations taken with a focal temperature of <= -120 C, since at higher temperatures the background cannot be modeled with their technique. This table was created by the HEASARC in July 2016 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/823/95">CDS Catalog J/ApJ/823/95</a> file catalog.dat. Some of the values for the name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC . 2016ApJ...823...95C https://heasarc.gsfc.nasa.gov/W3Browse/all/candelscxo.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=candelscxo& GET text/xml 180 99999 true 53.083637 -27.947222 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=candelscxo GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_candelscxo&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 X-ray public candelscxo CANDELS H-Band Selected Chandra Source Catalog source_number Sequential Identification Number for Each Source in the Catalog meta.id;src short nullable name Source Designation meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable error_radius Error on the X-Ray Centroid Position arcsec stat.error;pos double nullable fb_count_rate Count Rate in [0.5-7] keV Band ct/s phot.count;em.X-ray double nullable fb_count_rate_error 1-Sigma [0.5-7] keV Count Rate Error ct/s stat.error;phot.count;em.X-ray double nullable fb_flux Flux in [0.5-10] keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable fb_flux_error 1sigma [0.5-10] keV Flux Error erg/s/cm^2 stat.error;phot.flux;em.X-ray double nullable off_set Distance from the Best Optical Counterpart (arcsec) arcsec pos.angDistance double nullable f160w_mag F160W AB Magnitude phot.mag;em.IR.H double 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 sb_count_rate Count Rate in [0.5-2] keV Band ct/s phot.count;em.X-ray.soft double nullable can_prior_source_number CANDELS Identification of Optical Source Used as Prior for the X-Ray Detection meta.id int nullable phot_redshift_1 Photometric Redshift from Santini et al., 2015, Cat. J/ApJ/801/97 src.redshift.phot double nullable hardness_ratio_error Hardness Ratio Error stat.error;phot.flux;arith.ratio;em.X-ray double nullable hb_detect_likelihood -ln(p) Determined in the [2-7] keV Band stat.likelihood;phot.count;em.X-ray.medium double nullable redshift Spectroscopic Redshift from Santini et al., 2015, Cat. J/ApJ/801/97 (Spec_z) src.redshift double nullable hb_count_rate Count Rate in [2-7] keV Band ct/s phot.count;em.X-ray.medium double nullable prior_flag Flag to Determine the Reliability of the Association with a Prior meta.code short nullable sb_exposure Exposure Time in Soft Band s time.duration;obs.exposure;em.X-ray.soft double nullable bii Galactic Latitude degree pos.galactic.lat double nullable sb_detect_likelihood -ln(p) Determined in the [0.5-2] keV Band stat.likelihood;phot.count;em.X-ray.soft double nullable sb_flux Flux in [0.5-2] keV Band erg/s/cm^2 phot.flux;em.X-ray.soft double nullable xue_source_number Source Identification in Xuz et al., 2011, Cat. J/ApJS/195/10 meta.id short nullable id_flag Quality of the Identification Flag meta.code short nullable can_best_source_number CANDELS Identification of Primary Optical Counterpart of X-Ray Source from LR meta.id.cross int nullable sb_counts_error 1-Sigma [0.5-2] keV Counts Error ct stat.error;phot;em.X-ray.soft double nullable hb_counts_error 1-Sigma [2-7] keV Counts Error ct stat.error;phot;em.X-ray.medium double nullable candels_ra Best-Fit Right Ascension of the Best CANDELS Counterpart pos.eq.ra double nullable candels_dec Best-Fit Declination of the Best CANDELS Counterpart pos.eq.dec double nullable sb_counts Counts in [0.5-2] keV Band ct phot;em.X-ray.soft double nullable sb_count_rate_error 1-Sigma [0.5-2] keV Count Rate Error ct/s stat.error;phot.count;em.X-ray.soft double nullable hb_flux Flux in [2-10] keV Band erg/s/cm^2 phot.flux;em.X-ray.medium double nullable hb_flux_error 1-Sigma [2-10] keV Flux Error erg/s/cm^2 stat.error;phot.flux;em.X-ray.medium double nullable sb_flux_error 1sigma [0.5-20] keV Flux Error erg/s/cm^2 stat.error;phot.flux;em.X-ray.soft double nullable fb_counts_error 1-Sigma [0.5-7] keV Counts Error ct stat.error;phot;em.X-ray double nullable hardness_ratio Hardness Ratio phot.flux;arith.ratio;em.X-ray double nullable fb_counts Counts in [0.5-7] keV Band ct phot;em.X-ray double nullable can_2nd_source_number CANDELS Identification of 2nd Best Optical Counterpart of X-Ray Source from LR meta.id.cross int nullable hb_counts Counts in [2-7] keV Band ct phot;em.X-ray.medium double nullable hb_exposure Exposure Time in Hard Band s time.duration;obs.exposure;em.X-ray.medium double nullable lii Galactic Longitude degree pos.galactic.lon double nullable hb_count_rate_error 1-Sigma [2-7] keV Count Rate Error ct/s stat.error;phot.count;em.X-ray.medium double nullable fb_detect_likelihood -ln(p) Determined in the [0.5-7] keV Band stat.likelihood;phot.count;em.X-ray double nullable off_axis Off-Axis Angle arcmin instr.offset double nullable phot_redshift_2 Photometric Redshift from Hsu et al., 2014ApJ...796...60H src.redshift.phot double nullable