SDSSCXOQSO ivo://nasa.heasarc/sdsscxoqso NASA/GSFC HEASARC Green et al. 2026-05-08 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Quasar The authors have studied the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey (SDSS) that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project (ChaMP). Their highest-confidence matched sample (which this HEASARC table comprises) includes 1135 X-ray detected quasars in the redshift range 0.2 < z < 5.4, representing some 36 Msec of effective exposure. In their paper, the authors provide catalogs of QSO properties, and describe their novel method of calculating X-ray flux upper limits and effective sky coverage. Spectroscopic redshifts are available for about 1/3 of the detected sample; elsewhere, redshifts are estimated photometrically. The authors have detected 56 QSOs with redshift z > 3, substantially expanding the known sample. They find no evidence for evolution out to z ~ 5 for either the X-ray photon index Gamma or for the ratio of optical/UV to X-ray flux Alpha_ox. About 10% of detected QSOs show best-fit intrinsic absorbing columns greater than 10<sup>22</sup> cm<sup>-2</sup>, but the fraction might reach ~1/3 if most nondetections are absorbed. The authors confirm a significant correlation between Alpha_ox and optical luminosity, but it flattens or disappears for fainter (M_B >~ -23) active galactic nucleus (AGN) alone. They report significant hardening of Gamma both toward higher X-ray luminosity, and for relatively X-ray loud quasars. These trends may represent a relative increase in nonthermal X-ray emission, and their findings thereby strengthen analogies between Galactic black hole binaries and AGN. For uniformly selected subsamples of narrow-line Seyfert 1s and narrow absorption line QSOs, they find no evidence for unusual distributions of either Alpha_ox or Gamma. Much more information on the SDSS is available at the project's web site at <a href="http://www.sdss.org/">http://www.sdss.org/</a>. This table was created by the HEASARC in April 2009 based on the machine-readable version of Table 2 ('Properties of SDSS Quasars Detected by Chandra') which was obtained from the ApJ website. This is a service provided by NASA HEASARC . 2009ApJ...690..644G https://heasarc.gsfc.nasa.gov/W3Browse/all/sdsscxoqso.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=sdsscxoqso& GET text/xml 180 99999 true 340.69349 -9.712621 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=sdsscxoqso GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_sdsscxoqso&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 X-ray Optical public sdsscxoqso Sloan Digital Sky Survey Quasars Detected by Chandra 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 imag SDSS i Band PSF Magnitude (Dereddened) mag phot.mag;em.opt.I double nullable redshift Best Redshift src.redshift double nullable counts Net Counts in the 0.3-8keV range ct phot;em.X-ray double nullable counts_error RMS Uncertainty for Net Counts stat.error;phot;em.X-ray double nullable flux 0.5-8keV Flux (erg/cm^2/s) erg/s/cm^2 phot.flux;em.X-ray 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 off_axis Chandra Off-Axis Angle (arcmin) arcmin instr.offset double nullable log_2500a_luminosity Logarithm of 2500-Angstrom Luminosity (in erg/s/Hz) log(erg/s/Hz) phys.luminosity;em.UV.200-300nm double nullable class Browse Object Classification src.class short nullable lii Galactic Longitude degree pos.galactic.lon double nullable phot_redshift_upper Photometric Redshift Upper Limit src.redshift;stat.max double nullable nh_pos_err 90% Upper Error on Best Fit Intrinsic Absorbing HI Column Density H-atoms/cm^2 stat.error;phys.columnDensity double nullable phot_redshift Photometric Redshift src.redshift double nullable comments Comments Concerning Source meta.note char nullable nh_gal Galactic Absorbing H I Column Density H-atoms/cm^2 phys.columnDensity double nullable ref_redshift Reference for Spectroscopic Redshift: S=SDSS DR6, O=ChaMP, R=NED Reference meta.ref;src.redshift char nullable radio_loudness Radio Loudness meta.code;em.radio double nullable spect_index X-Ray Photon Energy Index spect.index;em.X-ray double nullable nh_neg_err 90% Lower Error on Best Fit Intrinsic Absorbing HI Column Density H-atoms/cm^2 stat.error;phys.columnDensity double nullable flux_20_cm_flag Boolean Flag [1] Indicates Multiple/Extended Radio Morphology in FIRST meta.code;phot.flux.density;em.radio.750-1500MHz short nullable opt_xray_spect_index Optical/X-Ray Spectral Index spect.index;em.opt;em.X-ray double nullable phot_redshift_prob Photometric Redshift Probability stat.probability;src.redshift double nullable exposure Vignetting-Corrected Exposure Time (s) s time.duration;obs.exposure double nullable nh Best Fit Intrinsic Absorbing HI Column Density H-atoms/cm^2 phys.columnDensity double nullable chandra_target Chandra PI Target meta.id short nullable spectral_class Spectral Classification [0123]: 1=BAL, 2=NAL, 3=NLS1 meta.code;src.class short nullable spect_index_pos_err 90% Upper Error Limit on X-Ray Photon Energy Index stat.error;spect.index;em.X-ray double nullable champ_srcid Chandra Multiwavelength Project (ChaMP) Source Identifier meta.id.cross char nullable log_2kev_luminosity Logarithm of 2keV Luminosity (in erg/s/Hz) log(erg/s/Hz) phys.luminosity;em.X-ray double nullable flux_20_cm Integrated 1.4GHz FIRST Radio Flux Density (mJy) mJy phot.flux.density;em.radio.750-1500MHz double nullable bii Galactic Latitude degree pos.galactic.lat double nullable sdss_obsid SDSS Object Identifier meta.id;obs char nullable spect_index_neg_err 90% Lower Error Limit on X-Ray Photon Energy Index stat.error;spect.index;em.X-ray double nullable phot_redshift_lower Photometric Redshift Lower Limit src.redshift;stat.min double nullable