J/ApJ/863/134ivo://CDS.VizieR/J/ApJ/863/134doi:10.26093/cds/vizier.18630134CDSHsyu T.Cooke R.J.Prochaska J.X.Bolte M.2021-01-25T11:03:41Z2019-11-27T15:04:27ZCDS support team

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

cds-question@unistra.frgalaxiesspectroscopychemical-abundancesredshiftedvisible-astronomysloan-photometryWe report a method of identifying candidate low-metallicity blue compact dwarf galaxies (BCDs) from the Sloan Digital Sky Survey (SDSS) imaging data, and present 3m Lick Observatory and 10m W.M. Keck Observatory optical spectroscopic observations of 94 new systems that have been discovered with this method. The candidate BCDs are selected from Data Release 12 (DR12) of SDSS on the basis of their photometric colors and morphologies. Using the Kast spectrometer on the 3m telescope, we confirm that the candidate low-metallicity BCDs are emission-line galaxies, and we make metallicity estimates using the empirical R and S calibration methods. Follow-up observations on a subset of the lowest-metallicity systems are made at Keck using the Low Resolution Imaging Spectrometer, which allow for a direct measurement of the oxygen abundance. We determine that 45 of the reported BCDs are low-metallicity candidates with 12+log(O/H)<=7.65, including six systems which are either confirmed or projected to be among the lowest-metallicity galaxies known, at 1/30 of the solar oxygen abundance, or 12+log(O/H)~7.20.2018ApJ...863..134Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/863/134CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)J/ApJS/147/29 : BRHalpha data of BCDs (Gil De Paz+, 2003)J/ApJS/156/345 : Surface photometry of BCD galaxies (Gil de Paz+, 2005)J/A+A/429/115 : JHK' photom. of Blue Compact Dwarf Galaxies (Noeske+, 2005)J/A+A/434/887 : HI data of blue compact dwarf galaxies (Huchtmeier+, 2005)J/ApJS/161/240 : High-ionization em. in metal-deficient BCDs (Thuan+, 2005)J/AJ/142/170 : the {alpha}.40 HI source catalog (Haynes+, 2011)J/ApJ/743/77 : Extremely metal-poor galaxies in SDSS (Morales-Luis+, 2011)J/A+A/546/A122 : SDSS extremely metal-poor galaxies (Izotov+, 2012)J/MNRAS/448/2687 : Blue diffuse dwarf galaxies spectrosc. data (James+, 2015)J/ApJ/819/73 : Metallicity evolution of COSMOS BCD sample (Lian+, 2016)J/ApJ/812/158 : Leo P RR Lyrae candidates & cumulative SFH (McQuinn+, 2015)J/other/RAA/17.41 : LAMOST metal-poor galaxies sample (Gao+, 2017)J/MNRAS/465/3977 : Blue diffuse dwarf galaxies (James+, 2017)J/ApJ/847/38 : Extreme emission line galaxies at z<~0.05 (Yang+, 2017)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/863/134https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/863/134http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/863/134https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/863/134https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/863/134http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/863/134GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/863/134/bcds (Observational, measured and derived properties of our blue compact dwarf galaxy (BCD) (tables 1, 2b and 5))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/863/134/bcds?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/863/134/bcds?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/863/134/bcds?GETtext/xml+votable180.050000true0.131041730.869250.0055555555555555566/705 2153 2251 2275 2314 2564 4758 5258 5585 5644 5698 5718 5726 6072 6364 6579 6619 6630 6634 7374 7400 7498 8320 8469 8470 8946 8975 9510 9669 9933 9992 10011 10237 10332 10445 10454 10607 10775 10961 11006 11018 11100 11111 11211 11366 11593 12615 12619 16973 16981 17238 17907 17958 18120 18250 18265 18364 18639 18689 18784 18873 19164 19171 19246 19289 19413 19644 19902 20020 20256 20406 20416 20423 22655 25916 26423 27066 27319 27857 27875 28022 28156 28441 28464 28473 31639 32409 36629 48855https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/863/134?format=asciiOpticaldefaultJ/ApJ/863/134/bcdsObservational, measured and derived properties of our blue compact dwarf galaxy (BCD) (tables 1, 2b and 5)SDSSSDSS-DR9 IAU name (column added by CDS)meta.id;meta.maincharNameTarget Namemeta.idcharprimaryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNelDisplay the emission line for this object (link to Table 2a)meta.ref.urlcharm_NameMultiple component ID on Namemeta.code.multipcharRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainObsObservation description; Telescope+Inst (1)meta.id;instrcharz[0.001/0.06] Spectroscopic redshiftsrc.redshiftfloatDist[7.2/240] Luminosity distance assuming a Planck cosmologyMpcpos.distancefloatgmag[16.5/22.9] The SDSS-DR12 g band AB magnitudemagphot.mag;em.opt.Bfloate_gmag[0/0.2] Uncertainty in gmagmagstat.error;phot.magfloatu-g[0.2/1.4] The (u-g) color indexmagphot.color;em.opt.U;em.opt.BfloatlogO[6.4/8.7] Oxygen abundance; 12+log(O/H) (2)log(Sun)phys.abundfloate_logO[0/0.4] Uncertainty in logOlog(Sun)stat.errorfloatFHb? H{beta} flux, F(H{beta}); in 10e-17erg/s/cm^2^ units1e+17mW.m**-2meta.unit;phot.flux;spect.linefloatnullablee_FHb? FHb uncertainty1e+17mW.m**-2stat.errorfloatnullableEWHb? H{beta} equivalent width in Angstoms0.1nmspect.line.eqWidthdoublenullablee_EWHb? EWHb uncertainty0.1nmstat.errordoublenullablecHb? H{beta} reddening corrections, c(H{beta})phys.absorptionfloatnullableEWHa? H{alpha} equivalent width in Angstroms0.1nmspect.line.eqWidthfloatnullableDM00[8.6/236.6]? Distance corrected for the local velocity field using Mould+ (2000ApJ...529..786M)Mpcpos.distance;pos.heliocentricfloatnullableBMag[-17.5/-10]? Absolute B band magnitude (1)magphys.magAbsfloatnullableLHa[0.04/57.4]? H{alpha} luminosity; in 1e+39erg/s units (2)log(1e+32W)phys.luminosity;em.line.Halphafloatnullablee_LHa[0.001/2]? Uncertainty in LHalog(1e+32W)stat.errorfloatnullableSFR[0.19/252]? Star Formation Rate (2)solMass/yrphys.SFRdoublenullablee_SFR[0.007/8.3]? Uncertainty in SFRsolMass/yrstat.error;phys.SFRfloatnullableM*[0.02/213.5]? Stellar mass (2)solMassphys.massfloatnullablee_M*[0.01/28]? Uncertainty in M*solMassstat.errorfloatnullableSloanDisplay the online SDSS data for the nearest objectmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/ApJ/863/134/table2aMeasured emission line fluxesLineLine identifiermeta.id;spect.lineNameTarget namemeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintm_NameMultiple component ID on Namemeta.code.multipcharlambdaWavelength(s) for Line0.1nmem.wlcharFLine[0/2510]? Emission line flux; corrected for the underlying stellar absorption and internal reddening, relative to H{beta}phot.fluxdoublenullablee_FLine[0.0001/355]? Uncertainty in Valuestat.errordoublenullable