J/ApJ/786/74ivo://CDS.VizieR/J/ApJ/786/74doi:10.26093/cds/vizier.17860074CDSFrebel A.Simon J.D.Kirby E.N.2017-09-04T08:19:12Z2017-08-04T11:18:23ZCDS support team

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

cds-question@unistra.frgalaxiesline-intensitiespopulation-ii-starsgiant-starsvisible-astronomysloan-photometrychemical-abundancesWe present Magellan/MIKE and Keck/HIRES high-resolution spectra of six red giant stars in the dwarf galaxy Segue 1. Including one additional Segue 1 star observed by Norris et al. (2010ApJ...722L.104N), high-resolution spectra have now been obtained for every red giant in Segue 1. Remarkably, three of these seven stars have metallicities below [Fe/H]=-3.5, suggesting that Segue 1 is the least chemically evolved galaxy known. We confirm previous medium-resolution analyses demonstrating that Segue 1 stars span a metallicity range of more than 2 dex, from [Fe/H]=-1.4 to [Fe/H]=-3.8. All of the Segue 1 stars are {alpha}-enhanced, with [{alpha}/Fe]~0.5. High {alpha}-element abundances are typical for metal-poor stars, but in every previously studied galaxy [{alpha}/Fe] declines for more metal-rich stars, which is typically interpreted as iron enrichment from supernova Ia. The absence of this signature in Segue 1 indicates that it was enriched exclusively by massive stars. Other light element abundance ratios in Segue 1, including carbon enhancement in the three most metal-poor stars, closely resemble those of metal-poor halo stars. Finally, we classify the most metal-rich star as a CH star given its large overabundances of carbon and s-process elements. The other six stars show remarkably low neutron-capture element abundances of [Sr/H]<-4.9 and [Ba/H]<-4.2, which are comparable to the lowest levels ever detected in halo stars. This suggests minimal neutron-capture enrichment, perhaps limited to a single r-process or weak s-process synthesizing event. Altogether, the chemical abundances of Segue 1 indicate no substantial chemical evolution, supporting the idea that it may be a surviving first galaxy that experienced only one burst of star formation.2014ApJ...786...74Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/786/74CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/692/1464 : Spectroscopy of Segue 1 (Geha+, 2009)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/786/74https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/786/74http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/786/74https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/786/74https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/786/74http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/786/74GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/786/74/table1 (Observing Details)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/786/74/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/786/74/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/786/74/table1?GETtext/xml+votable180.050000true151.81083316.0318060.0055555555555555566/44193.588997330618193e-19 4.653515163505597e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/786/74?format=asciiOpticaldefaultJ/ApJ/786/74/table1Observing DetailsSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameSDSS star's name (JHHMMSS+DDMMSS)meta.id;meta.maincharRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainObs.dateUT Date(s) of the observationtime.epoch;obscharSlitSlit widtharcsecspect.line.widthfloatTexpExposure timehtime.duration;obs.exposurefloatgmagSDSS g band magnitudemagphot.mag;em.opt.BfloatE(B-V)Reddeningmagphot.color.excessfloatS/N5300Signal-to-noise ratio at 5300 {AA} (1)stat.snrintS/N6000Signal-to-noise ratio 6000 {AA} (1)stat.snrintName1Star's name as written in table2.dat filemeta.idcharEWEquivalent widths and Log epsilon abundances from table2meta.ref.urlcharSloanDisplay the online SDSS data for the nearest objectmeta.ref.urlcharJ/ApJ/786/74/table2Equivalent width measurements of the Segue 1 starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDElementphys.atmol.elementcharWaveWavelength; Angstroms0.1nmem.wldoubleExPot? Excitation potentialeVphys.atmol.excitationfloatnullablelog(gf)? Log oscillator strengthphys.atmol.oscStrengthfloatnullableEW-J100714? Equivalent width of SDSS J100714+160154 (1)1e-13mspect.line.eqWidthfloatnullablef_EW-J100714[s] Flag indicating spectrum synthesis usedmeta.codechareps-J100714? Log epsilon abundance of SDSS J100714+160154phys.abundfloatnullableEW-J100710? Equivalent width of SDSS J100702+155055 (1)1e-13mspect.line.eqWidthfloatnullablef_EW-J100710[s] Flag indicating spectrum synthesis usedmeta.codecharl_eps-J100710[<] Limit flag on eps-J100710meta.code.errorchareps-J100710? Log epsilon abundance of SDSS J100702+155055phys.abundfloatnullableEW-J100702? Equivalent width of SDSS J100702+155055 (1)1e-13mspect.line.eqWidthfloatnullablef_EW-J100702[s] Flag indicating spectrum synthesis usedmeta.codecharl_eps-J100702[<] Limit flag on eps-J100702meta.code.errorchareps-J100702? Log epsilon abundance of SDSS J100702+155055phys.abundfloatnullableEW-J100742? Equivalent width of SDSS J100742+160106 (1)1e-13mspect.line.eqWidthfloatnullablef_EW-J100742[s] Flag indicating spectrum synthesis usedmeta.codecharl_eps-J100742[<] Limit flag on eps-J100742meta.code.errorchareps-J100742? Log epsilon abundance of SDSS J100742+160106phys.abundfloatnullableEW-J100652? Equivalent width of SDSS J100652+160235 (1)1e-13mspect.line.eqWidthfloatnullablef_EW-J100652[s] Flag indicating spectrum synthesis usedmeta.codecharl_eps-J100652[<] Limit flag on eps-J100652meta.code.errorchareps-J100652? Log epsilon abundance of SDSS J100652+160235phys.abundfloatnullableEW-J100639? Equivalent width of SDSS J100639+160008 (1)1e-13mspect.line.eqWidthfloatnullablef_EW-J100639[s] Flag indicating spectrum synthesis usedmeta.codecharl_eps-J100639[<] Limit flag on eps-J100639meta.code.errorchareps-J100639? Log epsilon abundance of SDSS J100639+160008phys.abundfloatnullable