J/A+A/620/A155ivo://CDS.VizieR/J/A+A/620/A155doi:10.26093/cds/vizier.36200155CDSMassari D.Helmi A.2020-06-25T14:42:15Z2018-12-11T08:09:39ZCDS support team

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

cds-question@unistra.frgalaxiesproper-motionsWe present mean absolute proper motion measurements for seven ultra- faint dwarf galaxies orbiting the Milky Way, namely Bootes III, Carina II, Grus II, Reticulum II, Sagittarius II, Segue 2 and Tucana IV. For four of these dwarfs our proper motion estimate is the first ever provided. The adopted astrometric data come from the second data release of the Gaia mission. We determine the mean proper motion for each galaxy starting from an initial guess of likely members, based either on radial velocity measurements or using stars on the Horizontal Branch identified in the Gaia (G_BP_-G_RP_, G) colour-magnitude diagram in the field of view towards the UFD. We then refine their membership iteratively using both astrometry and photometry. We take into account the full covariance matrix among the astrometric parameters when deriving the mean proper motions for these systems. Our procedure provides mean proper motions with typical uncertainties of ~0.1mas/yr, even for galaxies without prior spectroscopic information. In the case of Segue 2 we find that using radial velocity members only leads to biased results, presumably because of the small number of stars with measured radial velocities. Conclusions: our procedure allows to maximize the number of member stars per galaxy regardless of the existence of prior spectroscopic information, and can therefore be applied on any faint or distant stellar system within reach of Gaia.2018A&A...620A.155Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/620/A155CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/620/A155https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/620/A155http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/620/A155https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/620/A155https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/620/A155http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/620/A155GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/620/A155/table1 (*Results for the seven UFDs analysed in this paper)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/620/A155/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/620/A155/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/620/A155/table1?GETtext/xml+votable180.050000true114.1066-57.99910.005555555555555556Cone search capability for table J/A+A/620/A155/members (Stellar IDs and positions (table 2))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/620/A155/members?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/620/A155/members?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/620/A155/members?GETtext/xml+votable180.050000true114.049350695341-58.20793232021470.0055555555555555566/619 10308 10310 33626-33627 34856 34858 37615 46621 48771 48774https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/620/A155?format=asciidefaultJ/A+A/620/A155/table1*Results for the seven UFDs analysed in this paperSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameUltra-faint dwarf galaxy (UFD) namemeta.id;meta.maincharIG[RV HB] Initial guess (1)meta.codechar<pmRAcosDE>Mean proper motion along RA, pmRA*cosDEmas/yrpos.pm;stat.meanfloate_<pmRAcosDE>rms uncertainty on <pmRAcosDE>mas/yrstat.error;pos.pm;pos.eq.rafloat<pmDE>Mean proper motion along DEmas/yrpos.pm;stat.meanfloate_<pmDE>rms uncertainty on <pmDE>mas/yrstat.error;pos.pm;pos.eq.decfloatcovCovariance, cov(pmRAcosDE,pmDE)stat.covariancefloatNmembNumber of membersmeta.numberintSNameShort name of UDF galaxymeta.idchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainJ/A+A/620/A155/membersStellar IDs and positions (table 2)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameUltra-faint dwarf galaxy (UFD) short namemeta.idcharIDGaia source_idmeta.id;meta.mainRAICRSRight ascension (ICRS, epoch J2015.5)degpos.eq.ra;meta.mainDEICRSDeclination (ICRS, epoch J2015.5)degpos.eq.dec;meta.mainSimbadSimbad column added by the CDSmeta.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.decnullableindexed