J/ApJ/863/89ivo://CDS.VizieR/J/ApJ/863/89doi:10.26093/cds/vizier.18630089CDSSimon J.D.2021-01-25T09:21:26Z2019-08-30T15:30:56ZCDS support team

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

cds-question@unistra.frgalaxiesphotometryvisible-astronomyproper-motionsThe second data release from the Gaia mission (DR2) provides a comprehensive and unprecedented picture of the motions of astronomical sources in the plane of the sky, extending from the solar neighborhood to the outer reaches of the Milky Way. I present proper-motion measurements based on Gaia DR2 for 17 ultra-faint dwarf galaxies within 100kpc of the Milky Way. I compile the spectroscopically confirmed member stars in each dwarf bright enough for Gaia astrometry from the literature, producing member samples ranging from two stars in Triangulum II to 68 stars in Bootes I. From the spectroscopic member catalogs, I estimate the proper motion of each system. I find good agreement with the proper motions derived by the Gaia collaboration for Bootes I and Leo I. The tangential velocities for 14 of the 17 dwarfs are determined to better than 50km/s, more than doubling the sample of such measurements for Milky Way satellite galaxies. The orbital pericenters are well constrained, with a mean value of 38kpc. Only one satellite, Tucana III, is on an orbit passing within 15kpc of the Galactic center, suggesting that the remaining ultra-faint dwarfs are unlikely to have experienced severe tidal stripping. As a group, the ultra-faint dwarfs are on high-velocity, eccentric, retrograde trajectories, with nearly all of them having space motions exceeding 370km/s. A large majority of the objects are currently close to the pericenters of their orbits. In a low-mass (M_vir_=0.9x10^12^M_{sun}_) Milky Way potential, eight out of the 17 galaxies lack well-defined apocenters and appear likely to be on their first infall, indicating that the Milky Way mass may be larger than previously estimated or that many of the ultra-faint dwarfs are associated with the Magellanic Clouds. The median eccentricity of the ultra-faint dwarf orbits is 0.79, similar to the values seen in numerical simulations but distinct from the rounder orbits of the more luminous dwarf spheroidals.2018ApJ...863...89Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/863/89CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/337 : Gaia DR1 (Gaia Collaboration, 2016)I/345 : Gaia DR2 (Gaia Collaboration, 2018)J/MNRAS/354/708 : Leo I VI photometry (Bellazzini+, 2004)J/MNRAS/380/281 : Faint galactic satellites spectrosc. survey (Martin+, 2007)J/MNRAS/397/1748 : Spectroscopic study of Segue 2 (Belokurov+, 2009)J/ApJ/692/1464 : Spectroscopy of Segue 1 (Geha+, 2009)J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)J/ApJS/191/352 : Abundances in stars of MW dwarf satellites (Kirby+, 2010)J/ApJ/723/1632 : Abundance spreads in Bootes I and Segue 1 (Norris+, 2010)J/ApJ/711/350 : Metal-poor giant Boo-1137 abundances (Norris+, 2010)J/ApJ/736/146 : Radial velocities of stars in Bootes I (Koposov+, 2011)J/ApJ/741/100 : Proper motions of Leo II member stars (Lepine+, 2011)J/ApJ/733/46 : Velocity measurements in Segue 1 (Simon+, 2011)J/ApJ/752/42 : BV time series in Ursa Major II (Dall'Ora+, 2012)J/ApJ/756/79 : Opt. photom. in 3 Local Group dwarf galaxies (Sand+, 2012)J/ApJ/767/62 : RR Lyrae stars BV photometry in UMa I (Garofalo+, 2013)J/ApJ/763/61 : Abundances of 7 Bootees I red giant members (Gilmore+, 2013)J/ApJ/770/16 : Spectroscopic members of Segue 2 galaxy (Kirby+, 2013)J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)J/ApJ/786/74 : EW measurements of 6 Segue 1 red giants (Frebel+, 2014)J/A+A/562/A146 : Chemical abundances of 8 metal-poor stars (Ishigaki+, 2014)J/MNRAS/440/2665 : SDSS J021933.13+200830.2 spectroscopy (Roederer+, 2014)J/AJ/149/42 : Proper motion of Draco dwarf galaxy from HST (Pryor+, 2015)J/ApJ/808/95 : Spectroscopy of Reticulum II (Simon+, 2015)J/ApJ/826/110 : Boo-127 and Boo-980 high-resolution spectra (Frebel+, 2016)J/ApJ/830/93 : Ret II brightest red giant member abundances (Ji+, 2016)J/ApJ/817/41 : Abundances of 4 metal-poor red giants in BooII (Ji+, 2016)J/MNRAS/458/L59 : Draco II stars gi magnitudes & RVel. (Martin+, 2016)J/MNRAS/461/3702 : gi photometry of Bootes I (Roderick+, 2016)J/AJ/151/82 : 4 brightest red giants in Ret 2 (Roederer+, 2016)J/ApJ/819/53 : Magellan/M2FS spectroscopy of Tuc 2 & Grus 1 (Walker+, 2016)J/ApJ/838/44 : Abundances of TucIII brightest members (Hansen+, 2017)J/ApJ/838/83 : RVel, abundance & membership in TriII (Kirby+, 2017)J/ApJ/838/11 : Member stars in the MW satellite Tucana III (Simon+, 2017)J/ApJ/857/74 : Abundances of 7 new member stars in Tucana II (Chiti+, 2018)J/ApJ/857/145 : MagLiteS Carina II and Carina III spectroscopy (Li+, 2018)J/ApJ/852/99 : Abundances of 3 metal-poor stars in HorI (Nagasawa+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/863/89https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/863/89http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/863/89https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/863/89https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/863/89http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/863/89GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/863/89/table2 (Gaia DR2 proper motions of stars in ultra-faint dwarf galaxies)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/863/89/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/863/89/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/863/89/table2?GETtext/xml+votable180.050000true33.3189436.179380.005555555555555556Cone search capability for table J/ApJ/863/89/dgal (Ultra-faint dwarf parameters, Gaia DR2 data and orbits (Tables 1, 3 and 4))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/863/89/dgal?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/863/89/dgal?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/863/89/dgal?GETtext/xml+votable180.050000true33.322536.17830.0055555555555555565/2186 6/618 619 704 705 2341 2352 4417 4418 4419 4425 5939 5945 6021 6023 6032 7416 7417 8738 8739 8748 8750 11655 26487 28136 32916 33626 33627 33685 37613 37615 46126 46144 46145 46212https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/863/89?format=asciiOpticaldefaultJ/ApJ/863/89/table2Gaia DR2 proper motions of stars in ultra-faint dwarf galaxiesSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDStar identifiermeta.id;meta.maincharGalDwarf galaxy identifiermeta.idcharRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.maingmag[14.6/21.8] Apparent g band AB magnitudemagphot.mag;em.opt.Bfloatrmag[13.3/20.5] Apparent r band AB magnitudemagphot.mag;em.opt.RfloatpmRA[-51/51.6]? Proper motion along RA * cos(DE) (1)mas/yrpos.pm;pos.eq.rafloatnullablee_pmRA[0.04/1.8]? Uncertainty in pmRA (1)mas/yrstat.error;pos.pm;pos.eq.rafloatnullablepmDE[-65.6/20.5]? Proper motion along DE (1)mas/yrpos.pm;pos.eq.decfloatnullablee_pmDE[0.04/1.3]? Uncertainty in pmDE (1)mas/yrstat.error;pos.pm;pos.eq.decfloatnullableRefReference codes (see refs.dat file)meta.notecharf_IDSpectroscopic member flag on ID (2)meta.codecharCommAdditional commentmeta.notecharGaiaDisplay the PS1 data (II/349) within 2"meta.ref.urlcharSloanDisplay the online SDSS data for the nearest objectmeta.ref.urlcharJ/ApJ/863/89/refsReferences (table added by CDS)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRefReference codemeta.noteintBibCodeBibcode of the referencemeta.bib.bibcodecharAuthFirst author's name(s)meta.bib.authorcharCommVizieR catalogue referencemeta.notecharJ/ApJ/863/89/dgalUltra-faint dwarf parameters, Gaia DR2 data and orbits (Tables 1, 3 and 4)SimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameDwarf galaxy namemeta.id;meta.maincharRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainDist[21.5/97.3] Distancekpcpos.distance;pos.heliocentricfloate_Dist[0.4/12] Dist uncertaintykpcstat.errorfloatHRV[-381.7/477.2] Heliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloate_HRV[0.4/5.2] HRV uncertaintykm/sstat.errorfloatr_Pos[101/131] Position reference (see refs.dat file)meta.ref;pos.frameintr_Dist[101/131] Dist reference (see refs.dat file)meta.ref;pos.frameintr_HRV[102/132] HRV reference (see refs.dat file)meta.ref;pos.frameintGalAbbreviated galaxy name as in Table 2; column added by CDSmeta.idcharprimaryNs[2/68] Number of star membersmeta.numberintNNumber of stars for this galaxy field (link to Table 2)meta.numberintnullablepmRA[-2.6/3.9] Proper motion along RA * cos(DE) ({mu}_{alpha}_cos{delta})mas/yrpos.pm;pos.eq.rafloate_pmRA[0.03/0.4] pmRA uncertaintymas/yrstat.error;pos.pm;pos.eq.rafloatpmDE[-3.3/1.6] Proper motion along DE ({mu}_{delta}_)mas/yrpos.pm;pos.eq.decfloate_pmDE[0.03/0.4] pmDE uncertaintymas/yrstat.error;pos.pm;pos.eq.decfloatU[-262.3/340] U velocitykm/sphys.veloc;pos.cartesian.xfloatV[-544.8/-119.8] V velocitykm/sphys.veloc;pos.cartesian.yfloatW[-344.8/347.3] W velocitykm/sphys.veloc;pos.cartesian.zfloatRper[3/102] Orbital pericenterkpcpos.distance;src.orbitalinte_Rper[1/19] Negative uncertainty on Perickpcstat.errorintE_Rper[1/15] Positive uncertainty on Perickpcstat.error;stat.maxintRapo[49/1746] Orbital apocenterkpcpos.distance;src.orbitalinte_Rapo[5/1120] Negative uncertainty on Apockpcstat.errorintE_Rapo[6/1654] Positive uncertainty on Apockpcstat.error;stat.maxintecc[0.1/1] Orbital eccentricitysrc.orbital.eccentricityfloate_ecc[0.01/0.5] Negative uncertainty on eccstat.errorfloatE_ecc[0.01/0.7] Positive uncertainty on eccstat.error;stat.maxfloatl_PerLimit flag on Permeta.code.errorcharPer[0.7/10]? Orbital periodGyrtime.periodfloatnullableNEDNED column added by the CDSmeta.ref.urlchar