J/ApJ/833/270ivo://CDS.VizieR/J/ApJ/833/270doi:10.26093/cds/vizier.18330270CDSGlidden A.Cooper T.J.Cooksey K.L.Simcoe R.A.O'Meara J.M.2017-07-18T15:30:01Z2017-06-01T09:17:31ZCDS support team

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

cds-question@unistra.frquasarsredshiftedspectroscopychemical-abundancesWe measured metallicities for 33 z=3.4-4.2 absorption line systems drawn from a sample of HI-selected-Lyman limit systems (LLSs) identified in Sloan Digital Sky Survey (SDSS) quasar spectra and stratified based on metal line features. We obtained higher-resolution spectra with the Keck Echellette Spectrograph and Imager, selecting targets according to our stratification scheme in an effort to fully sample the LLS population metallicity distribution. We established a plausible range of HI column densities and measured column densities (or limits) for ions of carbon, silicon, and aluminum, finding ionization-corrected metallicities or upper limits. Interestingly, our ionization models were better constrained with enhanced {alpha}-to-aluminum abundances, with a median abundance ratio of [{alpha}/Al]=0.3. Measured metallicities were generally low, ranging from [M/H]=-3 to -1.68, with even lower metallicities likely for some systems with upper limits. Using survival statistics to incorporate limits, we constructed the cumulative distribution function (CDF) for LLS metallicities. Recent models of galaxy evolution propose that galaxies replenish their gas from the low-metallicity intergalactic medium (IGM) via high-density HI "flows" and eject enriched interstellar gas via outflows. Thus, there has been some expectation that LLSs at the peak of cosmic star formation (z~3) might have a bimodal metallicity distribution. We modeled our CDF as a mix of two Gaussian distributions, one reflecting the metallicity of the IGM and the other representative of the interstellar medium of star-forming galaxies. This bimodal distribution yielded a poor fit. A single Gaussian distribution better represented the sample with a low mean metallicity of [M/H]~-2.5.2016ApJ...833..270Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/833/270CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/221/2 : Keck+Magellan survey for LLSs. III. (Prochaska+, 2015)J/ApJ/775/78 : Lyman limit absorption systems in z~3 QSOs (Fumagalli+, 2013)J/ApJ/770/138 : Metallicities of Lyman limit systems and DLA (Lehner+, 2013)J/ApJ/765/137 : HST survey for Lyman limit systems. II. (O'Meara+, 2013)J/ApJ/755/89 : Metallicities of damped Ly{alpha} systems (Rafelski+, 2012)J/ApJ/736/48 : 48 Lyman break galaxies at z~3 in HUDF (Rafelski+, 2011)J/ApJ/718/392 : SDSS Lyman limit systems at z~3.5 (Prochaska+, 2010)J/ApJ/648/L97 : SDSS QSOs supersolar super-Lyman limit syst. (Prochaska+ 2006)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/833/270https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/833/270http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/833/270https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/833/270https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/833/270http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/833/270GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/833/270/table1 (Details for the Keck/ESI observations)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/833/270/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/833/270/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/833/270/table1?GETtext/xml+votable180.050000true18.4665-9.59750.0055555555555555566/4267 5239 5284 5372 5564 5946 6406 6418 6436 6576 8200 8621 8627 9143 9880 9988 10567 10692 11304 11308 17561 21885 23052 26015 26514 27524 27635 28067 28407 28482 28544 28652https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/833/270?format=asciiOpticaldefaultJ/ApJ/833/270/table1Details for the Keck/ESI observationsIDQSO Identifiermeta.id;meta.maincharprimaryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNdNumber of metal column density measurements for this QSOmeta.numberintnullablef_ID[ab] Flag on ID (1)meta.codecharRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainzqso[3.6/4.4] QSO redshiftsrc.redshift;pos.heliocentricfloatzlls[3.3/4.2] LLS redshiftsrc.redshift;pos.heliocentricfloatTier[1/3] Tier number (1=no metals) (2)meta.code.classintExpExposure timestime.duration;obs.exposurecharlogHIl[17/20] Lower limit on log H I column densitylog(cm**-2)phys.columnDensity;stat.minfloatlogHIu[17/20] Upper limit on log H I column densitylog(cm**-2)phys.columnDensity;stat.maxfloatl_ZLimit flag on Zmeta.code.error;src.redshiftcharZ[-3.6/-1.6] Metallicityphys.abund.Zfloate_Z[0.08/0.5]? Lower limit uncertainty in Zstat.error;src.redshiftfloatnullableE_Z[0.08/0.5]? Upper limit uncertainty in Zstat.error;stat.maxfloatnullablel_logULimit flag on logUmeta.code.errorcharlogU[-3/-1.3] Ionization parameterphys.ionizParamfloate_logU[0.06/0.3]? Lower limit uncertainty in logUstat.error;pos.cartesian.xfloatnullableE_logU[0.06/0.3]? Upper limit uncertainty in logUstat.error;stat.maxfloatnullablel_RatioLimit flag on Ratiometa.code.error;arith.ratiocharRatio[-1.4/0.8]? Log {alpha}/Al ratiophys.abundfloatnullablee_Ratio[0.09/0.2]? Lower limit uncertainty in Ratiostat.error;arith.ratiofloatnullableE_Ratio[0.09/0.2]? Upper limit uncertainty in Ratiostat.error;stat.maxfloatnullableSloanDisplay the online SDSS data for the nearest objectmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharNEDNED column added by the CDSmeta.ref.urlcharJ/ApJ/833/270/table2Metal column densitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDQSO Identifiermeta.id;meta.maincharzspec[3.3/4.2] Spectroscopic redshift (1)src.redshiftfloatlogNl[17/19.8] Log lower limit of H I column densitylog(cm**-2)phys.columnDensity;stat.minfloatlogNu[17.6/20] Log upper limit of H I column densitylog(cm**-2)phys.columnDensity;stat.maxfloatIonIon identifierphys.atmol.ionStagecharlambda[1260/1862]? Rest wavelength of Ion; Angstroms0.1nmem.wlintnullablel_logNLimit flag on logNmeta.code.errorcharlogN[11.5/14.8]? Log column density (2)log(cm**-2)phys.columnDensityfloatnullablee_logN[0.01/0.4]? Uncertainty in logNlog(cm**-2)stat.errorfloatnullablel_logNaLimit flag on logNameta.code.errorcharlogNa[11.5/14.8]? Log adopted column density (3)log(cm**-2)phys.columnDensityfloatnullablee_logNa[0.004/0.3]? Uncertainty in logNalog(cm**-2)stat.errorfloatnullablelogNp[11.6/15.8]? Log predicted column density (4)log(cm**-2)phys.columnDensityfloatnullablee_logNp[0.05/0.5]? Uncertainty in logNplog(cm**-2)stat.errorfloatnullable