J/A+A/661/A103ivo://CDS.VizieR/J/A+A/661/A103doi:10.26093/cds/vizier.36610103CDSMatsuno T.Koppelman H.H.Helmi A.Aoki W.Ishigaki M.N.Suda T.,Yuan Z.Hattori K.2022-11-13T16:56:09Z2022-05-10T11:47:43ZCDS support team

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

cds-question@unistra.frhalo-starschemical-abundancesspectroscopyline-intensitiesvisible-astronomySequoia is a retrograde kinematic substructures in the nearby Galactic halo, whose properties are a matter of debate. For example, previous studies do not necessarily agree on the chemical abundances of Sequoia stars, which are important for understanding its nature. We characterize the chemical properties of a sample of stars from Sequoia by determining high-precision abundances. Methods: We measure abundances of Na, Mg, Si, Ti, Cr, Mn, Ni, Zn, Y, and Ba from a differential abundance analysis on high signal-to-noise ratio, high-resolution spectra from new observations and from archival data. We compare precisely-measured chemical abundances of 12 Sequoia candidates with those of typical halo stars from literature, which include also stars from Gaia-Enceladus. This allows us to characterize Sequoia and compare it to another Galactic building block. The comparison is made after putting all the abundances onto the same scale using standard stars. There are significant difference in [Na/Fe], [Mg/Fe], [Ca/Fe], [Ti/Fe], [Zn/Fe], and [Y/Fe] between Sequoia and Gaia-Enceladus stars at -1.8<[Fe/H]<-1.4 in the sense that these abundance ratios are lower in Sequoia. These differences are similar to those seen between Gaia-Enceladus and in-situ stars at higher metallicity, suggesting that Sequoia is affected by type~Ia supernovae at lower metallicity than Gaia-Enceladus. We also confirm that the low [Mg/Fe] of Sequoia is seen in literature and in surveys, namely APOGEE DR16 and GALAH DR3, if the stars are kinematically selected in the same way. Sequoia stars have a distinct chemical abundance pattern and can be chemically separated from in-situ stars or Gaia-Enceladus stars if abundances are measured with sufficient precision, namely sigma([X/Fe])<0.07dex.2022A&A...661A.103Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/661/A103CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/661/A103https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/661/A103http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/661/A103https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/661/A103https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/661/A103http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/661/A103GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/661/A103/list (List of studied stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/661/A103/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/661/A103/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/661/A103/list?GETtext/xml+votable180.050000true262.94712536.465250.0055555555555555566/6226 7186 9495 18882 19989 20394 20680 21926 23705 23745 30553 32599 34466 39446 39692https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/661/A103?format=asciiOpticaldefaultJ/A+A/661/A103/listList of studied starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObjectObject name used in this studymeta.id;meta.maincharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainONameGaia EDR3 name (Gaia EDR3 NNNNNNNNNNNNNNNNNNN)meta.idcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/A+A/661/A103/lineLine listrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObjectObject name used in this studymeta.id;meta.maincharspeciesName of the speciesphys.atmol.elementcharlambdaWavelength0.1nmem.wldoublechiExcitation potentialeVphys.atmol.excitationfloatloggfloggf valuephys.atmol.oscStrengthfloatEWEquivalent width (m{AA})0.1pmspect.line.eqWidthfloate_EWUncertainty in equivalent width (m{AA})0.1pmstat.error;spect.line.eqWidthfloatAAbundance from this linephys.abundfloateAteffUncertainty in abundance due to effective temperaturestat.errorfloateAloggUncertainty in abundance due to surface gravitystat.errorfloateAvtUncertainty in abundance due to microturbulent velocitystat.errorfloateA[Fe/H]Uncertainty in abundance due to metallicitystat.errorfloateAEWUncertainty in abundance due to equivalent widths of this star and the reference starstat.errorcharsXUncertainty floorstat.errorfloatWeightWeight used to obtain the best estimate for the abundance of the speciesphys.atmol.weight;meta.modelleddouble