J/ApJ/826/110ivo://CDS.VizieR/J/ApJ/826/110doi:10.26093/cds/vizier.18260110CDSFrebel A.Norris J.E.Gilmore G.Wyse R.F.G.2017-12-06T07:38:29Z2016-10-26T15:51:31ZCDS support team

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

cds-question@unistra.frline-intensitieschemically-peculiar-starsgiant-starsWe present chemical abundance measurements of two metal-poor red giant stars in the ultra-faint dwarf galaxy Bootes I, based on Magellan/MIKE high-resolution spectra. For Boo-980, with [Fe/H]=-3.1 , we present the first elemental abundance measurements, while Boo-127, with [Fe/H]=-2.0 , shows abundances in good agreement with previous measurements. Light and iron-peak element abundance ratios in the two Bootes I stars, as well as those of most other Bootes I members, collected from the literature, closely resemble those of regular metal-poor halo stars. Neutron-capture element abundances Sr and Ba are systematically lower than the main halo trend and also show a significant abundance spread. Overall, this is similar to what has been found for other ultra-faint dwarf galaxies. We apply corrections to the carbon abundances (commensurate with stellar evolutionary status) of the entire sample and find 21% of stars to be carbon-enhanced metal-poor (CEMP) stars, compared to 13% without using the carbon correction. We reassess the metallicity distribution functions for the CEMP stars and non-CEMP stars, and confirm earlier claims that CEMP stars might belong to a different, earlier population. Applying a set of abundance criteria to test to what extent Bootes I could be a surviving first galaxy suggests that it is one of the earliest assembled systems that perhaps received gas from accretion from other clouds in the system, or from swallowing a first galaxy or building block type object. This resulted in the two stellar populations observable today.2016ApJ...826..110Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/826/110CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/817/41 : Abundances of 4 metal-poor red giants in BooII (Ji+, 2016)J/MNRAS/439/788 : Stromgren and Washington photometry in Boo I (Hughes+, 2014)J/A+A/562/A146 : Chemical abundances of 8 metal-poor stars (Ishigaki+, 2014)J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)J/ApJ/763/61 : Abundances of 7 red giant members of BootesI (Gilmore+, 2013)J/ApJ/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)J/ApJ/742/54 : CASH project II. Extremely metal-poor stars (Hollek+, 2011)J/ApJ/736/146 : Radial velocities of stars in Bootes I (Koposov+, 2011)J/ApJ/723/1632 : Abundance spreads in Bootes I and Segue 1 (Norris+, 2010)J/AN/331/474 : Abundances of metal-poor stars (Frebel, 2010)J/ApJ/711/350 : Metal-poor giant Boo-1137 abundances (Norris+, 2010)J/AJ/136/2321 : Washington photometry of Bootes I stars (Hughes+, 2008)J/MNRAS/380/281 : Faint galactic satellites spectrosc. survey (Martin+, 2007)J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)J/AJ/120/1841 : Abundances & Kinematics of Halo & Disk Stars (Fulbright 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/826/110https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/826/110http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/826/110https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/826/110https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/826/110http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/826/110GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/826/110/table1 (Observing details of Bootes I stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/826/110/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/826/110/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/826/110/table1?GETtext/xml+votable180.050000true209.802833313.71550.0055555555555555566/8744 8745https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/826/110?format=asciidefaultJ/ApJ/826/110/table1Observing details of Bootes I starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordint[NGW2008]Star namemeta.id;meta.mainintRAJ2000Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of declination (J2000)pos.eq.dec;meta.mainDateFirst UT date of observationtime.epoch;obsnullableDate2Other day(s) of observationtime.epoch;obscharSlitSlitarcsecinstr.setupfloatExpExposure timehtime.duration;obs.exposurefloatg0Corrected g-band magnitude from Norris+, 2008ApJ...689L.113Nmagphot.mag;arith.difffloat(g-r)0Corrected (g-r) color indexmagphot.color;em.opt.V;em.opt.RfloatS/N5300{AA} signal-to-noise ratiostat.snrintS/N26000{AA} signal-to-noise ratiostat.snrintEWsDisplay the equivalent width measurements for this starmeta.ref.urlcharSloanDisplay the online SDSS data for the nearest objectmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/ApJ/826/110/table2Equivalent width measurements of the Bootes I starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSpSpecies identifierphys.atmol.ionStagecharlambda[3423.7/6978.9] Wavelength; Angstroms0.1nmem.wldoubleExPot[0/4.6]? Excitation potentialeVphys.atmol.excitationfloatnullablef_ExPot[H] H:Flag indicating a hyperfine-structure linemeta.codecharlog(gf)[-5.7/0.7]? Log oscillator strengthphys.atmol.oscStrengthfloatnullableEW-980[15.9/199.2]? Equivalent width of Boo-980; milli-Angstroms1e-13mspect.line.eqWidthfloatnullablef_EW-980[s] s: Flag indicating spectrum synthesis usedmeta.codecharl_loge-980Limit flag on loge-980meta.code.errorcharloge-980[-2.2/5]? Log abundance in Boo-980log(Sun)phys.abundfloatnullableEW-127[15.4/394.2]? Equivalent width of Boo-127; milli-Angstroms1e-13mspect.line.eqWidthfloatnullablef_EW-127[s] s: Flag indicating spectrum synthesis usedmeta.codecharl_loge-127Limit flag on loge-127meta.code.errorcharloge-127[-0.7/6.4]? Log abundance in Boo-127log(Sun)phys.abundfloatnullable