J/ApJ/651/61ivo://CDS.VizieR/J/ApJ/651/61doi:10.26093/cds/vizier.16510061CDSHennawi J.F.Prochaska J.X.Burles S.Strauss M.A.Richards G.T.,Schlegel D.J.Fan X.Schneider D.P.Zakamska N.L.Oguri M.Gunn J.E.,Lupton R.H.Brinkmann J.2018-01-04T08:22:32Z2008-12-16T12:54:24ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frquasarsredshiftedvisible-astronomysloan-photometryWith close pairs of quasars at different redshifts, a background quasar sight line can be used to study a foreground quasar's environment in absorption. We search 149 moderate-resolution background quasar spectra from Gemini, Keck, the MMT, and the SDSS to survey Lyman limit systems (LLSs) and damped Ly{alpha} systems (DLAs) in the vicinity of 1.8<z<4.0 luminous foreground quasars. A sample of 27 new quasar-absorber pairs is uncovered with column densities 10^17.2^cm^-2^<NH<10^20.9^cm^-2^ and transverse (proper) distances of 22h^-1^kpc<R<1.7h^-1^Mpc from the foreground quasars.2006ApJ...651...61Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/651/61CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/282 : The SDSS Photometric Catalog, Release 6 (Adelman-McCarthy+, 2007)http://www.sdss.org : SDSS Home Pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/651/61https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/651/61http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/651/61https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/651/61https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/651/61http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/651/61GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/651/61/photom (Coordinates and photometry for projected quasar pairs in tables 1 and 2)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/651/61/photom?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/651/61/photom?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/651/61/photom?GETtext/xml+votable180.050000true9.18104178.66233330.0055555555555555566/4238 4920 4925 5494 5976 6409 6441 9323 9446 9978 11400 11803 11907 11908 17741 17751 18416 19537 19692 23190 23191 23210 25931 25953 26202 27654 27770 28606 32680 367832.040811542443644e-19 6.090060298487514e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/651/61?format=asciiOpticaldefaultJ/ApJ/651/61/photomCoordinates and photometry for projected quasar pairs in tables 1 and 2recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameQuasar name (SDSS JHHMM+DDMM or 2QZ JHHMM+DDMM)meta.id;meta.maincharm_Name[A-E] Multiplicity index on Name (1)meta.code.multipcharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainzSpectroscopic redshiftsrc.redshiftfloatumagExtinction-corrected SDSS u magnitudemagphot.mag;em.opt.UfloatgmagExtinction-corrected SDSS g magnitudemagphot.mag;em.opt.BfloatrmagExtinction-corrected SDSS r magnitudemagphot.mag;em.opt.RfloatimagExtinction-corrected SDSS i magnitudemagphot.mag;em.opt.IfloatzmagExtinction-corrected SDSS z magnitudemagphot.mag;em.opt.IfloatTypeSimbad column added by the CDSmeta.codecharSystemSystem name ((SDSS JHHMM+DDMM)meta.id.parentcharSDSSDisplay the SDSS data for this quasarmeta.ref.urlcharJ/ApJ/651/61/ALSConfirmed or Tentative optically thick absorption-line systems near foreground quasarsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTypeSimbad column added by the CDSmeta.codecharSystemSystem name (SDSS JHHMM+DDMM)meta.id;meta.maincharprimaryn_System[a-d] Note on System (1)meta.notecharzbgBackground quasar redshiftsrc.redshiftfloatzfgForeground quasar redshiftsrc.redshiftfloatDtheAngular separation of the quasar pair sight lines (2)arcsecpos.angDistancefloatRRadius (in (h^-1^kpc)kpcphys.size.radiusintzabsAbsorber redshiftsrc.redshiftfloat|DV|Velocity difference between the absorber redshift and our best estimate of the redshift of the foreground quasarkm/sphys.veloc;arith.diffintDVfgEstimated error on the foreground quasar redshiftkm/sstat.errorintl_logNHILimit flag on logNHImeta.code.errorcharlogNHI? Column density of the absorber from our fit to the HI profilelog(cm**-2)stat.weightfloatnullablee_logNHI? rms uncertainty on logNHIlog(cm**-2)stat.errorfloatnullablegUVMaximum enhancement of the quasar's ionizing photon flux over that of the extragalactic ionizing background, at the location of the background quasar sight line, assuming that gUV=1+F_QSO_/F_UVB_ the quasar emission is isotropicphot.flux;arith.ratiointn_zfgEmission line that was centered to determine foreground quasar redshift (zfg)meta.notecharobs.fgInstrument used to observed foreground quasarmeta.id;instrcharobs.bgInstrument used to observed background quasarmeta.id;instrchar