J/ApJ/767/134ivo://CDS.VizieR/J/ApJ/767/134doi:10.26093/cds/vizier.17670134CDSVargas L.C.Geha M.Kirby E.N.Simon J.D.2017-10-18T08:23:59Z2014-12-17T09:56:33ZCDS support team

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

cds-question@unistra.frchemical-abundancesgiant-starsgalaxiesradial-velocityThe Milky Way ultra-faint dwarf (UFD) galaxies contain some of the oldest, most metal-poor stars in the universe. We present [Mg/Fe], [Si/Fe], [Ca/Fe], [Ti/Fe], and mean [{alpha}/Fe] abundance ratios for 61 individual red giant branch stars across eight UFDs. This is the largest sample of alpha abundances published to date in galaxies with absolute magnitudes M_V_>-8, including the first measurements for Segue 1, Canes Venatici II, Ursa Major I, and Leo T. Abundances were determined via medium-resolution Keck/DEIMOS spectroscopy and spectral synthesis. The sample spans the metallicity range -3.4<[Fe/H]<-1.1. With the possible exception of Segue 1 and Ursa Major II, the individual UFDs show on average lower [{alpha}/Fe] at higher metallicities, consistent with enrichment from Type Ia supernovae. Thus, even the faintest galaxies have undergone at least a limited level of chemical self-enrichment. Together with recent photometric studies, this suggests that star formation in the UFDs was not a single burst, but instead lasted at least as much as the minimum time delay of the onset of Type Ia supernovae (~100Myr) and less than ~2Gyr. We further show that the combined population of UFDs has an [{alpha}/Fe] abundance pattern that is inconsistent with a flat, Galactic halo-like alpha abundance trend, and is also qualitatively different from that of the more luminous CVn I dSph, which does show a hint of a plateau at very low [Fe/H].2013ApJ...767..134Vhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/767/134CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/570/A61 : PM-selected stars of Hercules UFD (Fabrizio+, 2014)J/ApJ/763/61 : Abundances of 7 red giant members of BootesI (Gilmore+, 2013)J/ApJ/756/108 : HST VI phot. of variable stars in Leo T (Clementini+, 2012)J/ApJ/756/79 : Optical phot. in 3 Local Group dwarf galaxies (Sand+, 2012)J/ApJ/752/42 : BV time series in Ursa Major II (Dall'Ora+, 2012)J/ApJ/733/46 : Velocity measurements in Segue 1 (Simon+, 2011)J/AJ/141/90 : SEGUE stellar parameter pipeline. V. (Lee+, 2011)J/A+A/511/L10 : Abundances and space velocities of 94 stars (Nissen+, 2010)J/ApJ/723/1632 : Abundance spreads in Bootes I and Segue 1 (Norris+, 2010)J/ApJ/719/931 : Chemical evolution of the UMi dSph (Cohen+, 2010)J/ApJ/711/350 : Metal-poor giant Boo-1137 abundances (Norris+, 2010)J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)J/ApJS/191/352 : Abundances in stars of MW dwarf satellites (Kirby+, 2010)J/AJ/137/272 : Space velocities orbits in the Milky Way halo (Roederer+ 2009)J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)J/ApJ/692/1464 : Spectroscopy of Segue 1 (Geha+, 2009)J/ApJ/682/1217 : Abundances in red giants in 7 globular clusters (Kirby+, 2008)J/AJ/128/1177 : Galactic stellar abundances (Venn+, 2004)J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/767/134https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/767/134http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/767/134https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/767/134https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/767/134http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/767/134GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/767/134/table1 (Ultra-faint dwarf (UFD) galaxies studied)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/767/134/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/767/134/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/767/134/table1?GETtext/xml+votable180.050000true151.763333316.07361110.005555555555555556Cone search capability for table J/ApJ/767/134/table2 (*Abundance results)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/767/134/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/767/134/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/767/134/table2?GETtext/xml+votable180.050000true151.718041716.04327780.0055555555555555566/4410 4419 6021 6023 6032 7416 7417 10444 10769 10771 26980 28136 31692https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/767/134?format=asciiOpticaldefaultJ/ApJ/767/134/table1Ultra-faint dwarf (UFD) galaxies studiedSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameUFD galaxy namemeta.numbercharNNumber of red giant members with abundances (table 2)meta.numberintnullableDist[23/417] Heliocentric distance (R_helio_) (1)kpcpos.distanceintf_Dist[*] UFD added at CDS (2)meta.codecharRV[-128/208]? Radial velocity (3)km/sphys.veloc;pos.heliocentricintnullablee_RV[0.9/2]? RV uncertaintykm/sstat.errorfloatnullableSig[3.3/7.6]? ~3{sigma} of the systemic UFD velocity ({sigma}V) (3)km/sphys.velocfloatnullablee_Sig[0.8/1.7]? Sig uncertaintykm/sstat.errorfloatnullableVMag[-7.1/-1.5]? Absolute V-band magnitude (4)magphot.mag;em.opt.VfloatnullableNMg[0/3]? Number of Mg measurementsmeta.numberintnullableNSi[2/7]? Number of Si measurementsmeta.numberintnullableNCa[1/13]? Number of Ca measurementsmeta.numberintnullableNTi[3/8]? Number of Ti measurementsmeta.numberintnullableNa[4/13]? Number of [{alpha}/Fe]_avg_ measurementsmeta.numberintnullable<[Fe/H]>[-2.9/-1.9]? Mean metallicity (5)log(Sun)phys.abund.Fefloatnullablee_<[Fe/H]>[0.05/0.2]? <[Fe/H]> uncertaintylog(Sun)stat.error;phys.abund.FefloatnullableUFDAbbreviated name as in table 2 (column added by CDS)meta.idcharNEDSimbad column added by the CDSmeta.ref.urlchar_RAPositions from SIMBAD database (right ascension part)degpos.eq.ra;meta.main_DEPositions from SIMBAD database (declination part)degpos.eq.dec;meta.mainJ/ApJ/767/134/table2*Abundance resultsUFDName of UFD Galaxymeta.id.parentcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.main[Fe/H][-3.5/-0.8] Iron abundance relative to the Sunlog(Sun)phys.abund.Fefloate_[Fe/H]Uncertainty in [Fe/H]log(Sun)stat.error;phys.abund.Fefloat[a/Fe]{alpha}-elements abundance [{alpha}/Fe]log(Sun)phys.abundfloatE_[a/Fe]Upper limit uncertainty in [a/Fe]log(Sun)stat.error;stat.maxfloate_[a/Fe]Lower limit uncertainty in [a/Fe]log(Sun)stat.error;phys.abundfloat[Mg/Fe]? Magnesium-to-iron abundance ratiolog(Sun)phys.abund;arith.ratiofloatnullableE_[Mg/Fe]? Upper limit uncertainty in [Mg/Fe]log(Sun)stat.error;stat.maxfloatnullablee_[Mg/Fe]? Lower limit uncertainty in [Mg/Fe]log(Sun)stat.error;phys.abundfloatnullable[Si/Fe]? Silicon-to-iron abundance ratiolog(Sun)phys.abund;arith.ratiofloatnullableE_[Si/Fe]? Upper limit uncertainty in [Si/Fe]log(Sun)stat.error;stat.maxfloatnullablee_[Si/Fe]? Lower limit uncertainty in [Si/Fe]log(Sun)stat.error;phys.abundfloatnullable[Ca/Fe]? Calcium-to-iron abundance ratiolog(Sun)phys.abund;arith.ratiofloatnullableE_[Ca/Fe]? Upper limit uncertainty in [Ca/Fe]log(Sun)stat.error;stat.maxfloatnullablee_[Ca/Fe]? Lower limit uncertainty in [Ca/Fe]log(Sun)stat.error;phys.abundfloatnullable[Ti/Fe]? Titanium-to-iron abundance ratiolog(Sun)phys.abund;arith.ratiofloatnullableE_[Ti/Fe]? Upper limit uncertainty in [Ti/Fe]log(Sun)stat.error;stat.maxfloatnullablee_[Ti/Fe]? Lower limit uncertainty in [Ti/Fe]log(Sun)stat.error;phys.abundfloatnullableA[a] Flag for possibly anomalous abundance ratio (see Section 5.3)meta.codecharK10Simbad column added by the CDSmeta.ref.urlintnullable