J/A+A/698/A53ivo://CDS.VizieR/J/A+A/698/A53doi:10.26093/cds/vizier.36980053CDSTolstoy E.Battaglia G.Arroyo-Polonio J.M.Brown A.G.A.van Essen T.,Massari D.Skuladottir A.Irwin M.J.Taibi S.Pritchard J.2025-08-11T20:02:07Z2025-06-03T10:43:14ZCDS support team

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

cds-question@unistra.frgalaxiesgiant-starsradial-velocityspectroscopyvisible-astronomyThe Sextans dwarf spheroidal galaxy has been challenging to study in a comprehensive way as it is highly extended on the sky, with an uncertain but large tidal radius of between 80-160 arcminutes (or 3-4kpc), and an extremely low central surface brightness of Sigma_V_~26.2mag/arcsec^2^. Here, we present a new homogeneous survey of 41 VLT/FLAMES multi-fibre spectroscopic pointings that contain 2108 individual spectra, and combined with Gaia DR3 photometry and astrometry we present vlos measurements for 333 individual red giant branch stars that are consistent with membership in the Sextans dwarf spheroidal galaxy. In addition, we provide the metallicity, [Fe/H], determined from the two strongest CaII triplet lines, for 312 of these stars. We look again at the global characteristics of Sextans, deriving a mean line-of-sight velocity of <vlos>=+227.1km/s and a mean metallicity of <[Fe/H]>=-2.37. The metallicity distribution is clearly double-peaked, with the highest peak at [Fe/H]=-2.81 and another broader peak at [Fe/H]~=-2.09. Thus, it appears that Sextans hosts two populations and the superposition leads to a radial variation in the mean metallicity, with the more metal-rich population being centrally concentrated. In addition, there is an intriguing group of nine probable members in the outer region of Sextans at higher [Fe/H] than the mean in this region. If these stars were confirmed as members, they would eliminate the metallicity gradient. We also look again at the colour-magnitude diagram of the resolved stellar population in Sextans, and at the relation between Sextans and the intriguingly nearby globular cluster, Pal 3. The global properties of Sextans have not changed significantly compared to previous studies, but they are now more precise, and the sample of known members in the outer regions is now more complete.2025A&A...698A..53Thttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/698/A53CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)J/ApJS/268/19 : M2FS + Hectochelle spectra of dSph in MW halo (Walker+, 2023)J/A+A/675/A49 : vlos of Sculptor dSph red giants (Tolstoy+, 2023)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/698/A53https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/698/A53http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/698/A53https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/698/A53https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/698/A53http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/698/A53GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/698/A53/tabled1 (*Full measurements of the 604 likely members of the Sextans dSph)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/698/A53/tabled1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/698/A53/tabled1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/698/A53/tabled1?GETtext/xml+votable180.050000true153.55501-0.703580.005555555555555556Cone search capability for table J/A+A/698/A53/tabled2 (Gaia DR3 and spectroscopic information for the stars for which we have FLAMES observations but either are very clear non-members on the basis of their spectroscopic vlos or their spectroscopic measurements were not found to be reliable enough)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/698/A53/tabled2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/698/A53/tabled2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/698/A53/tabled2?GETtext/xml+votable180.050000true151.4010.066560.0055555555555555565/6801 6803-6804 6806 6/26862 27201 27203 27208-27209 27220 27222 27237 272481.9867573869263685e-19 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/698/A53?format=asciiOpticaldefaultJ/A+A/698/A53/tabled1*Full measurements of the 604 likely members of the Sextans dSphrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGaiaDR3Gaia DR3 identification numbermeta.id;meta.mainRA_ICRSGaia right ascension (ICRS) at Ep=2016.0degpos.eq.ra;meta.mainDE_ICRSGaia declination (ICRS) at Ep=2016.0degpos.eq.dec;meta.mainGmagGaia G magnitudemagphot.mag;em.optfloatBPmagGaia BP magnitudemagphot.mag;em.opt.BfloatRPmagGaia RP magnitudemagphot.mag;em.opt.RfloatplxGaia parallaxmaspos.parallax.trigfloat_RA.icrsRight ascension (ICRS) at Epoch=J2000, proper motions taken into accountdegpos.eq.raindexed_DE.icrsDeclination (ICRS) at Epoch=J2000, proper motions taken into accountdegpos.eq.decindexede_plxGaia parallax errormasstat.error;pos.parallaxfloatpmRAGaia proper motion along RAmas/yrpos.pm;pos.eq.rafloate_pmRAGaia proper motion along RA errormas/yrstat.error;pos.pm;pos.eq.rafloatpmDEGaia proper motion along DEmas/yrpos.pm;pos.eq.decfloate_pmDEGaia proper motion along DE errormas/yrstat.error;pos.pm;pos.eq.decfloatFLAMESfieldName of the VLT/FLAMES pointingobs.fieldcharSpecNameName of object in VLT/FLAMES pointingmeta.idcharNspec? Number of individual VLT/FLAMES spectra combinedmeta.numberintnullableCombSN? Combined signal to noise for the FLAMES spectra (1)stat.snrfloatnullableVel? Average radial velocity for the FLAMES spectra (2)km/sphys.velocfloatnullablee_Vel? Average radial velocity error for the FLAMES spectra (2)km/sstat.errorfloatnullablevarVel? Variance of radial velocity measurements, if Nspec>1 (2)km/sstat.variancefloatnullable[Fe/H]? Average [Fe/H] for FLAMES spectra (3)phys.abund.Fe;stat.meanfloatnullablee_[Fe/H]? Error on average [Fe/H] for FLAMES spectra (3)stat.error;phys.abund.Fefloatnullablevar[Fe/H]? Variance of [Fe/H] measurements, if Nspec>1 (3)stat.variancefloatnullablePmem[0/1] Probability of membership from Battaglia et al. (2022A&A...657A..54B, Cat. J/A+A/657/A54) analysis (4)stat.probabilityfloatNotesPrevious observations (5)meta.notecharJ/A+A/698/A53/tabled2Gaia DR3 and spectroscopic information for the stars for which we have FLAMES observations but either are very clear non-members on the basis of their spectroscopic vlos or their spectroscopic measurements were not found to be reliable enoughrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGaiaDR3? Gaia DR3 identifiermeta.id;meta.mainnullableRA_ICRSGaia right ascension (ICRS) at Ep=2016.0degpos.eq.ra;meta.mainDE_ICRSGaia declination (ICRS) at Ep=2016.0degpos.eq.dec;meta.mainFLAMESfieldFLAMES field nameobs.fieldcharSpecnameFLAMES target namemeta.idcharGmag? Gaia DR3 G magnitudemagphot.mag;em.optdoublenullableS/NSignal-to-noise ratiostat.snrdoubleVelHelioenctric radial velocitykm/sphys.velocfloatPmem[0/1]? Probability of membershipstat.probabilityfloatnullableCmemMembership class (1)meta.code.classcharNotesWhy rejectedmeta.notechar