J/A+A/546/A122ivo://CDS.VizieR/J/A+A/546/A122doi:10.26093/cds/vizier.35460122CDSIzotov Y.I.Thuan T.X.Guseva N.G.2018-01-04T08:21:33Z2013-01-11T10:25:29ZCDS support team

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

cds-question@unistra.frh-ii-regionschemical-abundancesline-intensitiesWe present 6.5-m MMT and 3.5m APO spectrophotometry of 69 HII regions in 42 low-metallicity emission-line galaxies, selected from the data release 7 of the Sloan Digital Sky Survey to have mostly [OIII]{lambda}4959/H{beta}<~1 and [NII]{lambda}6583/H{beta}<~0.1. The electron temperature-sensitive emission line [OIII]{lambda}4363 is detected in 53 HII regions allowing a direct abundance determination. The oxygen abundance in the remaining 16 HII regions is derived using a semi-empirical method. The oxygen abundance of the galaxies in our sample ranges from 12+logO/H~7.1 to ~7.9, with 14 HII regions in 7 galaxies with 12+logO/H<=7.35. In 5 of the latter galaxies, the oxygen abundance is derived here for the first time. Including other known extremely metal-deficient emission-line galaxies from the literature, e.g. SBS 0335-052W, SBS 0335-052E and I Zw 18, we have compiled a sample of the 17 most metal-deficient (with 12+logO/H<=7.35) emission-line galaxies known in the local universe. There appears to be a metallicity floor at 12+log O/H~6.9, suggesting that the matter from which dwarf emission-line galaxies formed was pre-enriched to that level by e.g. Population III stars.2012A&A...546A.122Ihttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/546/A122CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/511/639 : Abundances in blue compact galaxies (Izotov+, 1999)J/ApJ/602/200 : HII regions abundances in blue compact galaxies (Izotov+ 2004)J/ApJS/161/240 : High-ionization emission in metal-deficient BCDs (Thuan+ 2005)J/A+A/448/955 : Abundances of emission galaxies in SDSS-DR3 (Izotov+, 2006)J/ApJ/662/15 : Abundances in extragalactic HII regions (Izotov+, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/546/A122https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/546/A122http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/546/A122https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/546/A122https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/546/A122http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/546/A122GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/546/A122/table1 (General characteristics of galaxies)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/546/A122/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/546/A122/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/546/A122/table1?GETtext/xml+votable180.050000true18.41854170.87753890.0055555555555555566/4121 4756 4823 4891 4933 5283 5359 5419 5428 5459 5501 5633 5842 5964 6010 6488 7400 7431 8165 9407 10494 10666 10722 10755 10768 10881 10905 10965 10999 11428 11783 17833 18011 18858 26162 26253 27409 27818 28200 28311 28496https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/546/A122?format=asciiOpticaldefaultJ/A+A/546/A122/table1General characteristics of galaxiesSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSam[abc] Sample (1)src.samplecharGalaxyGalaxy namemeta.id;meta.maincharprimaryRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainzRedshiftsrc.redshiftdoubleDistDistanceMpcpos.distance;pos.heliocentricfloatBand[Bg] Band (SDSS g or B)instr.bandpasscharmagB or g magnitudemagphot.magfloate_magrms uncertainty on magmagstat.error;phot.magfloatONameOther namesmeta.idcharRef? Reference (2)meta.ref;pos.frameintnullableSloanDisplay the SDSS data for this galaxymeta.ref.urlcharNEDSimbad column added by the CDSmeta.refcharJ/A+A/546/A122/tablebH{beta} parametersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSamSample: a=3.5m APO, b=low-resolution MMT, c=medium-resolution MMTmeta.idcharGalaxyGalaxy namemeta.id;meta.maincharC(Hb)H{beta} extinction coefficientphys.absorptionfloatF(Hb)Uncorrected H{beta} flux1e-19W.m**-2phot.flux;em.line.HbetafloatEW(Hb)H{beta} equivalent width0.1nmspect.line.eqWidth;em.line.HbetafloatEW(abs)Equivalent width of the hydrogen absorption stellar lines0.1nmspect.line.eqWidthfloatJ/A+A/546/A122/tableaEmission line intensitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSamSample: a=3.5m APO, b=low-resolution MMT, c=medium-resolution MMTmeta.idcharGalaxyGalaxy namemeta.id;meta.maincharlambdaWavelength0.1nmem.wlintIonIon designationphys.atmol.ionStageI(lambda)? Emission line intensity [I(H{beta})=100]spect.line.intensity;arith.ratiofloatnullablee_I(lambda)? rms uncertainty on I(lambda)stat.errorfloatnullableJ/A+A/546/A122/tablecIonic and total heavy element abundancesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSamSample: a=3.5m APO, b=low-resolution MMT, c=medium-resolution MMTmeta.idcharGalaxyGalaxy namemeta.id;meta.maincharMet[ab] Method: a=direct, b=semi-empiricalmeta.notecharParamProperty namemeta.id;stat.fit.paramValueParam valuestat.valuedoublee_Value? rms uncertainty on valuestat.error;stat.valuedoublenullable