J/ApJ/902/51ivo://CDS.VizieR/J/ApJ/902/51doi:10.26093/cds/vizier.19020051CDSEscala I.Kirby E.N.Gilbert K.M.Wojno J.Cunningham E.C.,Guhathakurta P.2023-08-16T15:25:54Z2022-05-02T13:26:42ZCDS support team

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

cds-question@unistra.frgalaxiesmetallicityradial-velocitygiant-starsvisible-astronomyspectroscopyWe present measurements of [Fe/H] and [{alpha}/Fe] for 128 individual red giant branch stars (RGB) in the stellar halo of M31, including its Giant Stellar Stream (GSS), obtained using spectral synthesis of low- and medium-resolution Keck/DEIMOS spectroscopy (R~3000 and 6000, respectively). We observed four fields in M31's stellar halo (at projected radii of 9, 18, 23, and 31kpc), as well as two fields in the GSS (at 33kpc). In combination with existing literature measurements, we have increased the sample size of [Fe/H] and [{alpha}/Fe] measurements from 101 to a total of 229 individual M31 RGB stars. From this sample, we investigate the chemical abundance properties of M31's inner halo, finding <[Fe/H]>=-1.08+/-0.04 and <[{alpha}/Fe]>=0.40+/-0.03. Between 8 and 34kpc, the inner halo has a steep [Fe/H] gradient (-0.025+/-0.002dex/kpc) and negligible [{alpha}/Fe] gradient, where substructure in the inner halo is systematically more metal-rich than the smooth component of the halo at a given projected distance. Although the chemical abundances of the inner stellar halo are largely inconsistent with that of present-day dwarf spheroidal (dSph) satellite galaxies of M31, we identified 22 RGB stars kinematically associated with the smooth component of the stellar halo that have chemical abundance patterns similar to M31 dSphs. We discuss formation scenarios for M31's halo, concluding that these dSph-like stars may have been accreted from galaxies of similar stellar mass and star formation history, or of higher stellar mass and similar star formation efficiency.2020ApJ...902...51Ehttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/902/51CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)J/AJ/124/234 : M31 outer halo UBVRI photometry & metallicity (Reitzel+, 2002)J/AJ/128/1177 : Galactic stellar abundances (Venn+, 2004)J/ApJ/682/1217 : Abundances in red giants in 7 globular clusters (Kirby+, 2008)J/ApJS/184/152 : Deep optical photometry in M31 (Brown+, 2009)J/AJ/138/1243 : The star formation history of the LMC (Harris+, 2009)J/A+A/511/L10 : Abundances and space velocities of 94 stars (Nissen+, 2010)J/ApJ/743/19 : Phot. of variable star candidates in M31 (Clementini+, 2011)J/A+A/530/A15 : Abundances of 94 stars (Nissen+, 2011)J/ApJ/753/64 : Detailed abundances for 97 metal-poor stars (Ishigaki+, 2012)J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)J/ApJ/752/45 : SPLASH: Stellar spectrosc. of M31 satellites (Tollerud+, 2012)J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)J/ApJ/788/72 : Observed sample of z~0.7 massive galaxies (Gallazzi+, 2014)J/ApJ/790/73 : Iron & alpha abund. of RGBs in M31 satellites (Vargas+, 2014)J/ApJ/798/77 : Metallicity of RGB stars in 6 M31 dwarf galaxies (Ho+, 2015)J/AJ/151/144 : ASPCAP weights for 15 APOGEE chemical elements (Garcia+, 2016)J/ApJ/825/50 : Variable stars in M31 & M33. III. YSGs & RSGs (Gordon+, 2016)J/ApJ/852/50 : Gal. halo with APOGEE. II. Abund. (Fernandez-Alvar+, 2018)J/ApJ/852/49 : Properties of metal-poor stars in APOGEE DR13 (Hayes+, 2018)J/ApJ/856/15 : Stellar mass-metallicity relation. I. (Leethochawalit+, 2018)J/ApJ/868/55 : Large-scale structure of M31 halo. II. (McConnachie+, 2018)J/ApJ/883/128 : alpha & Fe abund. in the giant stellar stream (Gilbert+, 2019)J/ApJ/885/100 : Star mass-metallicity relation. II. (Leethochawalit+, 2019)J/ApJ/889/177 : RGB abund. in the disk, stream & halo of M31 (Escala+, 2020)J/AJ/159/46 : Elemental abund. of 416 stars in 5 dSphs of M31 (Kirby+, 2020)J/ApJ/895/78 : [Fe/H] and [{alpha}/Fe] in M31 dwarf galaxies (Wojno+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/902/51https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/902/51http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/902/51https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/902/51https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/902/51http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/902/51GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/902/51/table4 (Catalog of stellar parameters and abundances)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/902/51/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/902/51/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/902/51/table4?GETtext/xml+votable180.050000true11.434791740.90416670.005555555555555556Cone search capability for table J/ApJ/902/51/table1 (Deep DEIMOS observations in M31)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/902/51/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/902/51/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/902/51/table1?GETtext/xml+votable180.050000true11.445916740.94963890.0055555555555555566/2614-2615 2621 2623 2658 20470https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/902/51?format=asciiOpticaldefaultJ/ApJ/902/51/table4Catalog of stellar parameters and abundancesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFieldM31 fieldmeta.id;obs.fieldchar[EKG2020][1092174/8005126] Object identifiermeta.id;meta.mainintRAJ2000[0] Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000[38/41] Degree of Declination (J2000)pos.eq.dec;meta.mainHRV[-647.2/-142.6] Heliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloatSN[4/56] Signal-to-noise per Angstrom10nmstat.snrintTeff[3609/4825] Effective temperatureKphys.temperature.effectiveinte_Teff[2/162] Uncertainty in TeffKstat.error;phys.temperature.effectiveintlogg[0.28/1.51] Surface gravity, loglog(cm.s**-2)phys.gravityfloat[Fe/H][-3.2/-0.09] Metallicityphys.abund.Zfloate_[Fe/H][0.1/0.4] Uncertainty in [Fe/H]stat.error;phys.abund.Fefloat[a/Fe][-0.5/1.1]? {alpha} element abundancephys.atmol.elementfloatnullablee_[a/Fe][0.13/0.5]? Uncertainty in [a/Fe]stat.error;phys.abundfloatnullableSimbadSimbad column added by the CDSmeta.ref.urlcharJ/ApJ/902/51/table1Deep DEIMOS observations in M31FieldM31 field identifierobs.fieldcharprimaryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDist[9/33] Projected radial distance, r_proj_, from the center of M31kpcpos.distanceintCompKinematical component: "Halo" or "GSS" (Giant Stellar Stream)meta.notecharRAJ2000Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of declination (J2000)pos.eq.dec;meta.mainPA[-20/178.2] Position angle (east of north)degpos.posAngfloatGratingGratingmeta.notecharSlitSlitmask name (1)meta.id;obscharDateDate of observation (UT)time.epochnullableSeeing[0.43/0.88] Average seeingarcsecinstr.obsty.seeing;stat.meanfloatAirmass[1.06/1.52] Average airmass, Xobs.airMassfloatExp[0.43/3.5] Exposure time per slitmaskhtime.duration;obs.exposurefloatNs[67/143]? Number of stars targeted per slitmaskmeta.numberintnullableNstarsNumber of stars in this field (link to Table 4)meta.numberintnullable