J/A+A/633/A36ivo://CDS.VizieR/J/A+A/633/A36doi:10.26093/cds/vizier.36330036CDSMassari D.Helmi A.Mucciarelli A.Sales L.V.Spina L.Tolstoy E.2021-10-01T08:43:17Z2020-01-09T08:17:58ZCDS support team

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

cds-question@unistra.frgalaxiesvisible-astronomyradial-velocityproper-motionsWe present the first three-dimensional internal motions for individual stars in the Draco dwarf spheroidal galaxy. By combining first epoch Hubble Space Telescope observations and second epoch Gaia Data Release 2 positions we measured the proper motions of 149 sources in the direction of Draco. We determined the line-of-sight velocities of a sub-sample of 81 red giant branch stars using medium resolution spectra acquired with the DEIMOS spectrograph at the Keck II telescope. Altogether this resulted in a final sample of 45 members of Draco with high-precision and accurate 3D motions, which we publish as a table in this paper. With this high-quality dataset we determined the velocity dispersions at a projected distance of ~120pc from the centre of Draco to be sigma_R_=11.0^+2.1^_-1.5_km/s, sigma_T_=9.9^+2.3^_-3.1_km/s and sigma_LOS_=9.0^+1.1^_-1.1_ km/s in the projected radial, tangential and line-of-sight directions. This results in a velocity anisotropy beta=0.25^+0.47^_-1.38_ at r>120pc. Tighter constraints can be obtained using the spherical Jeans equations and assuming constant anisotropy and NFW mass profiles, as well as that the 3D velocity dispersion should be lower than ~1/3 of the escape velocity of the system. In this case, we constrain the maximum circular velocity V_max_ of Draco to be in the range of 10.2-17.0km/s. The corresponding mass range is in good agreement with previous estimates based on line-of-sight velocities only. Our Jeans modelling supports the case for a cuspy dark matter profile in this galaxy. Firmer conclusions may be drawn by applying more sophisticated models on this dataset and with upcoming data releases.2020A&A...633A..36Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/633/A36CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)J/MNRAS/448/2717 : Bayesian analysis of resolved stellar spectra (Walker+ 2015)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/633/A36https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/633/A36http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/633/A36https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/633/A36https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/633/A36http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/633/A36GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/633/A36/table2 (Parameters for the radial velocity sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/633/A36/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/633/A36/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/633/A36/table2?GETtext/xml+votable180.050000true259.845124957.94789080.005555555555555556Cone search capability for table J/A+A/633/A36/table3 (Measurements for the with 3D kinematics)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/633/A36/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/633/A36/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/633/A36/table3?GETtext/xml+votable180.050000true259.841715477957.98408603210.0055555555555555566/101831.9867573869263685e-19 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/633/A36?format=asciiOpticaldefaultJ/A+A/633/A36/table2Parameters for the radial velocity sampleSimbadNameSimbad column added by the CDSmeta.idcharnullableRA_ICRSRight ascension (ICRS) at Ep=2015.5degpos.eq.ra;meta.mainrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDE_ICRSDeclination (ICRS) at Ep=2015.5degpos.eq.dec;meta.mainGmagGaia G magnitudemagphot.mag;em.optfloatvlosRadial velocitykm/sphys.veloc;pos.heliocentricfloate_vlosRadial velocity uncertaintykm/sstat.errorfloatFlag[0/2]? Flag (1)meta.code.errorintnullableGRD2Display the Gaia DR2 (Cat. I/345) datameta.ref.urlchar_RA.icrsRight ascension (ICRS) at Epoch=J2015.5 (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) at Epoch=J2015.5 (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.decnullableindexedJ/A+A/633/A36/table3Measurements for the with 3D kinematicsSimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRA_ICRSRight ascension (ICRS) at Ep=2015.5degpos.eq.ra;meta.mainDE_ICRSDeclination (ICRS) at Ep=2015.5degpos.eq.dec;meta.mainGmagGaia G magnitudemagphot.mag;em.optfloatpmRA*Proper motion along RA, mu_alpha_*cos(delta)mas/yrpos.pm;pos.eq.rafloate_pmRA*mu_alpha_*cos(delta) uncertaintymas/yrstat.error;pos.pm;pos.eq.rafloatpmDEProper motion alongDE, mu_delta_mas/yrpos.pm;pos.eq.decfloate_pmDEmu_delta_ uncertaintymas/yrstat.error;pos.pm;pos.eq.decfloatvlosRadial velocitykm/sphys.veloc;pos.heliocentricfloate_vlosRadial velocity uncertaintykm/sstat.errorfloatGRD2Display the Gaia DR2 (Cat. I/345) datameta.ref.urlchar_RA.icrsRight ascension (ICRS) at Epoch=J2000, proper motions taken into accountdegpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) at Epoch=J2000, proper motions taken into accountdegpos.eq.decnullableindexed