J/ApJ/859/L8ivo://CDS.VizieR/J/ApJ/859/L8doi:10.26093/cds/vizier.18599008CDSHayes C.R.Majewski S.R.Hasselquist S.Beaton R.L.Cunha K.,Smith V.V.Price-Whelan A.M.Anguiano B.Beers T.C.Carrera R.,Fernandez-Trincado J.G.Frinchaboy P.M.Garcia-Hernandez D.A.Lane R.R.,Nidever D.L.Nitschelm C.Roman-Lopes A.Zamora O.2018-06-22T09:16:57Z2018-06-22T10:16:28ZCDS support team

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

cds-question@unistra.frmilky-way-galaxygiant-starspopulation-ii-starschemical-abundancesastrometryphotometryradial-velocityThe nature of the Triangulum-Andromeda (TriAnd) system has been debated since the discovery of this distant, low-latitude Milky Way (MW) overdensity more than a decade ago. Explanations for its origin are either as a halo substructure from the disruption of a dwarf galaxy, or a distant extension of the Galactic disk. We test these hypotheses using the chemical abundances of a dozen TriAnd members from the Sloan Digital Sky Survey-IV's (SDSS-IV's) 14th Data Release (DR14) of Apache Point Observatory Galactic Evolution Experiment (APOGEE) data to compare to APOGEE abundances of stars with similar metallicity from both the Sagittarius (Sgr) dSph and the outer MW disk. We find that TriAnd stars are chemically distinct from Sgr across a variety of elements, (C+N), Mg, K, Ca, Mn, and Ni, with a separation in [X/Fe] of about 0.1 to 0.4dex depending on the element. Instead, the TriAnd stars, with a median metallicity of about -0.8, exhibit chemical abundance ratios similar to those of the lowest metallicity ([Fe/H]~-0.7) stars in the outer Galactic disk, and are consistent with expectations of extrapolated chemical gradients in the outer disk of the MW. These results suggest that TriAnd is associated with the MW disk, and, therefore, that the disk extends to this overdensity-i.e., past a Galactocentric radius of 24kpc-albeit vertically perturbed about 7kpc below the nominal disk midplane in this region of the Galaxy.2018ApJ...859L...8Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/859/L8CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/852/49 : Properties of metal-poor stars in APOGEE DR13 (Hayes+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/859/L8https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/859/L8http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/859/L8https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/859/L8https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/859/L8http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/859/L8GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/859/L8/table1 (Properties of TriAnd Stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/859/L8/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/859/L8/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/859/L8/table1?GETtext/xml+votable180.050000true11.9714988940.292843060.0055555555555555566/1004 1007 1016 2269 2346 2369 2438 2615 2621 2634 2658 136318.650015785639275e-20 1.7003137259100215e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/859/L8?format=asciidefaultJ/ApJ/859/L8/table1Properties of TriAnd StarsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAPOGEEAPOGEE identifier (2MHHMMSSss+DDMMSSs)meta.id;meta.maincharRAJ2000Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainGLONGalactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latdoubleJmag2MASS J band magnitudemagphot.mag;em.IR.JfloatHmag2MASS H band magnitudemagphot.mag;em.IR.HfloatKsmag2MASS Ks band magnitudemagphot.mag;em.IR.KfloatDistHeliocentric distancekpcpos.distancedoublee_DistUncertainty in Distkpcstat.errordoubleHRVHeliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricdoublee_HRVUncertainty in HRVkm/sstat.errordoubleTeffEffective surface temperatureKphys.temperature.effectivedoublee_TeffUncertainty in TeffKstat.error;phys.temperature.effectivedoublelogglog surface gravitylog(cm.s**-2)phys.gravitydoublee_loggUncertainty in logglog(cm.s**-2)stat.errordoubleVturbMicroturbulent velocitykm/sphys.velocdoubleVmacroMacroturbulent velocitykm/sphys.velocdouble[Fe/H]log Fe/H abundancelog(Sun)phys.abund.Fedoublee_[Fe/H]Uncertainty in [Fe/H]log(Sun)stat.error;phys.abund.Fedouble[CN/Fe]log (C+N)/Fe abundancelog(Sun)phys.abunddoublee_[CN/Fe]Uncertainty in [CN/Fe]log(Sun)stat.error;phys.abunddouble[Mg/Fe]log Mg/Fe abundancelog(Sun)phys.abunddoublee_[Mg/Fe]Uncertainty in [Mg/Fe]log(Sun)stat.error;phys.abunddouble[K/Fe]log K/Fe abundancelog(Sun)phys.abunddoublee_[K/Fe]Uncertainty in [K/Fe]log(Sun)stat.error;phys.abunddouble[Ca/Fe]log Ca/Fe abundancelog(Sun)phys.abunddoublee_[Ca/Fe]Uncertainty in [Ca/Fe]log(Sun)stat.error;phys.abunddouble[Mn/Fe]log Mn/Fe abundancelog(Sun)phys.abunddoublee_[Mn/Fe]Uncertainty in [Mn/Fe]log(Sun)stat.error;phys.abunddouble[Ni/Fe]log Ni/Fe abundancelog(Sun)phys.abunddoublee_[Ni/Fe]Uncertainty in [Ni/Fe]log(Sun)stat.error;phys.abunddouble2MDisplay the 2MASS data (Cutri et al. 2003, Cat. II/246)meta.ref.urlchar