J/ApJ/883/163ivo://CDS.VizieR/J/ApJ/883/163doi:10.26093/cds/vizier.18830163CDSBecker G.D.Pettini M.Rafelski M.D'Odorico V.Boera E.,Christensen L.Cupani G.Ellison S.L.Farina E.P.Fumagalli M.,Lopez S.Neeleman M.Ryan-Weber E.V.Worseck G.2021-07-05T09:05:33Z2021-04-12T09:44:48ZCDS support team

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

cds-question@unistra.frintergalactic-mediumquasarsline-intensitiesredshiftedspectroscopyWe present a survey for metal absorption systems traced by neutral oxygen over 3.2<z<6.5. Our survey uses Keck/ESI and VLT/X-Shooter spectra of 199 QSOs with redshifts up to 6.6. In total, we detect 74 OI absorbers, of which 57 are separated from the background QSO by more than 5000km/s. We use a maximum likelihood approach to fit the distribution of OI{lambda}1302 equivalent widths in bins of redshift and from this determine the evolution in number density of absorbers with W_1302_>0.05{AA}, of which there are 49 nonproximate systems in our sample. We find that the number density does not monotonically increase with decreasing redshift, as would naively be expected from the buildup of metal-enriched circumgalactic gas with time. The number density over 4.9<z<5.7 is a factor of 1.7-4.1 lower (68% confidence) than that over 5.7<z<6.5, with a lower value at z<5.7 favored with 99% confidence. This decrease suggests that the fraction of metals in a low-ionization phase is larger at z~6 than at lower redshifts. Absorption from highly ionized metals traced by CIV is also weaker in higher-redshift OI systems, supporting this picture. The evolution of OI absorbers implies that metal-enriched circumgalactic gas at z~6 is undergoing an ionization transition driven by a strengthening ultraviolet background. This in turn suggests that the reionization of the diffuse intergalactic medium may still be ongoing at or only recently ended by this epoch.2019ApJ...883..163Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/883/163CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/eso : ESO Science Archive Catalog (ESO, 1991-2021)VII/258 : Quasars and Active Galactic Nuclei (13th Ed.) (Veron+ 2010)VII/283 : The Million Quasars (Milliquas) catalog (6.3) (Flesch, 2019)VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)J/A+A/473/791 : CIV absorption in DLAs and sub-DLAs systems (Fox+, 2007)J/A+A/508/133 : Damped Lyman{alpha} absorbers in z>4 QSOs (Guimaraes+, 2009)J/ApJ/718/392 : SDSS Lyman limit systems at z~3.5 (Prochaska+, 2010)J/ApJ/761/112 : High-redshift MgII abs. QSOs with FIRE (Matejek+, 2012)J/ApJ/755/89 : Metallicities of damped Ly{alpha} systems (Rafelski+, 2012)J/ApJ/763/37 : Metals in SDSS QSOs. I. 1.5<z<4.5 CIV abs. (Cooksey+, 2013)J/ApJS/206/4 : SED & bol. corrections for luminous QSOs (Krawczyk+, 2013)J/MNRAS/435/1198 : z~6 QSOs CIV doublet absorption systems (D'Odorico+, 2013)J/MNRAS/462/3285 : XQ-100. X-shooter quasar spectra (Perrotta+, 2016)J/MNRAS/455/1043 : SDSS DLA and absorber quasar samples (Murphy+, 2016)J/MNRAS/456/4488 : XQ-100 survey neutral gas (Sanchez-Ramirez+, 2016)J/ApJS/227/11 : PS1 z>5.6 quasars follow-up (Banados+, 2016)J/MNRAS/472/1850 : Detecting damped Ly{alpha} absorbers (Garnett+, 2017)J/ApJ/869/123 : Keck Lyman continuum spectroscopic survey (Steidel+, 2018)J/other/RAA/19.29 : Compilation of known QSOs for Gaia (Liao+, 2019)J/A+A/624/A145 : Large Quasar Astrometric Catalog 5, LQAC-5 (Souchay+, 2019)J/A+A/631/A78 : QSOs at z~6 spectral cubes (Stanley+, 2019)J/ApJS/249/17 : SDSS QSO DR14 spectral properties (Rakshit+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/883/163https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/883/163http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/883/163https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/883/163https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/883/163http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/883/163GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/883/163/table1 (QSO spectra used in this work)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/883/163/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/883/163/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/883/163/table1?GETtext/xml+votable180.050000true220.70884119.33375940.0055555555555555566/33 42 424 514 592 717 2187 2584 4157 4169 4177 4224 4233 4242 4263 4267 4279 4369 4466 4507 4648 4662 4761 4872 5016 5124 5153 5440 5630 6219 7326 8215 8218 8277 8344 8345 8627 8713 8722 8765 8819 9231 9373 9469 9831 10246 10456 10756 12567 12576 13418 16417 16554 16589 16641 16656 16666 16894 17068 17236 17252 17358 17382 17649 17679 17691 17735 17751 17818 17820 17872 17898 17989 18007 18061 18088 18155 18200 18209 18222 18242 18310 18381 18414 18466 18499 18627 18638 18642 18706 18751 19008 19067 19137 19214 19490 19507 19622 19759 20037 20116 20273 21872 21885 21989 22393 23150 23191 23210 25597 25827 25844 25863 26037 26167 26233 26239 26369 26375 26492 26520 26524 26560 26596 26650 26846 26869 26882 26962 26973 26976 27041 27057 27062 27083 27232 27286 27359 27436 27440 27445 27484 27498 27511 27524 27542 27564 27588 27646 27700 27781 27790 27846 27901 27917 28171 28173 28312 28332 30036 30039 30836 31313 31659 31706 32466 33746 34262 34271 34375 34762 34809 34850 35002 35100 35241 35304 35615 35759 35764 35770 35895 36217 36271 36300 36466 36834 37533 43983 44391 44463 44743 45460 46589 46983 48715 48899https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/883/163?format=asciidefaultJ/ApJ/883/163/table2Rest-frame equivalent width measurements for 60 QSOsf_CII-1334Flag on CII-1334 (3)meta.codecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintz[3.24/6.26] Absorber redshiftsrc.redshiftfloatf_zFlag(s) on z (1)meta.codecharTargetQSO identifiermeta.id;meta.maincharOI-1302[0.02/0.9] Rest-frame OI{lambda}1302 equivalent width (2)0.1nmspect.line.eqWidthfloate_OI-1302[0.001/0.04] Uncertainty in OI-13020.1nmstat.errorfloatf_OI-1302Flag on OI-1302 (3)meta.codecharl_CII-1334Limit flag on CII-1334meta.code.errorcharCII-1334[0.02/1.2]? Rest-frame CII{lambda}1334 equivalent width (2)0.1nmspect.line.eqWidthfloatnullablee_CII-1334[0.001/0.04]? Uncertainty in CII-13340.1nmstat.errorfloatnullablel_SiII-1260Limit flag on SiII-1260meta.code.errorcharSiII-1260[0.04/1.1]? Rest-frame SiII{lambda}1260 equivalent width (2)0.1nmspect.line.eqWidthfloatnullablee_SiII-1260[0.001/0.03]? Uncertainty in SiII-12600.1nmstat.errorfloatnullablef_SiII-1260Flag on SiII-1260 (3)meta.codecharl_SiII-1304Limit flag on SiII-1304meta.code.errorcharSiII-1304[0.007/0.8] Rest-frame SiII{lambda}1304 equivalent width (2)0.1nmspect.line.eqWidthfloate_SiII-1304[0.001/0.04]? Uncertainty in SiII-13040.1nmstat.errorfloatnullablef_SiII-1304Flag on SiII-1304 (3)meta.codecharl_SiII-1526Limit flag on SiII-1526meta.code.errorcharSiII-1526[0.008/0.9]? Rest-frame Si II 1526 equivalent width (2)0.1nmspect.line.eqWidthfloatnullablee_SiII-1526[0.001/0.07]? Uncertainty in SiII-15260.1nmstat.errorfloatnullablef_SiII-1526Flag on SiII-1526 (3)meta.codecharMgII-2796[0.1/2.5]? Rest-frame MgII{lambda}2796 equivalent width (2)0.1nmspect.line.eqWidthfloatnullablee_MgII-2796[0.002/0.09]? Uncertainty in MgII-27960.1nmstat.errorfloatnullablef_MgII-2796Flag(s) on MgII-2796 (3)meta.codecharl_MgII-2803Limit flag on MgII-2803meta.code.errorcharMgII-2803[0.07/2]? Rest-frame MgII{lambda}2803 equivalent width (2)0.1nmspect.line.eqWidthfloatnullablee_MgII-2803[0.002/0.15]? Uncertainty in MgII-28030.1nmstat.errorfloatnullablef_MgII-2803Flag on MgII-2803 (3)meta.codecharl_SIV-1393Limit flag on SIV-1393meta.code.errorcharSIV-1393[0.009/0.7]? Rest-frame SIV{lambda}1393 equivalent width (2)0.1nmspect.line.eqWidthfloatnullablee_SIV-1393[0.002/0.1]? Uncertainty in SIV-13930.1nmstat.errorfloatnullablef_SIV-1393Flag on SIV-1393 (3)meta.codecharl_SiIV-1402Limit flag on SiIV-1402meta.code.errorcharSiIV-1402[0.006/0.65]? Rest-frame SIV{lambda}1402 equivalent width (2)0.1nmspect.line.eqWidthfloatnullablee_SiIV-1402[0.003/0.04]? Uncertainty in SiIV-14020.1nmstat.errorfloatnullablef_SiIV-1402Flag SiIV-1402 (3)meta.codecharl_CIV-1548Limit flag on CIV-1548meta.code.errorcharCIV-1548[0.004/1]? Rest-frame CIV{lambda}1548 equivalent width (2)0.1nmspect.line.eqWidthfloatnullablee_CIV-1548[0.002/0.08]? Uncertainty in CIV-15480.1nmstat.errorfloatnullablef_CIV-1548Flag(s) on CIV-1548 (3)meta.codecharl_CIV-1550Limit flag on CIV-1550meta.code.errorcharCIV-1550[0.003/0.7]? Rest-frame CIV{lambda}1550 equivalent width (2)0.1nmspect.line.eqWidthfloatnullablee_CIV-1550[0.002/0.08]? Uncertainty in CIV-15500.1nmstat.errorfloatnullablef_CIV-1550Flag on CIV-1550 (3)meta.codecharFNum[11/84] Corresponding figure numbermeta.bib.figintJ/ApJ/883/163/table1QSO spectra used in this workSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSetSubsample identifier (column added by CDS) (1)meta.codeintSeq[1/199] Running sequence numbermeta.idintTargetQSO identifiermeta.idcharprimaryz[3.52/6.65] QSO redshift based on the apparent start of the Ly{alpha} forestsrc.redshiftfloatInstInstrument used for the OI searchinstr.setupcharS/N[10.4/237.2] Signal-to-noise ratio per 30km/s near rest wavelength 1285{AA}stat.snrfloatEWOI[0.019/0.22] OI{lambda}1302 rest-frame equivalent width in {AA} at which the OI search is 50% complete (see Section 3.3)0.1nmspect.line.eqWidthfloatNzNumber of absorber redshift measurements for this quasar (link to Table 2)meta.numberintnullableSloanDisplay the online SDSS-DR14 online data for the nearest objectmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main