J/ApJ/892/137ivo://CDS.VizieR/J/ApJ/892/137doi:10.26093/cds/vizier.18920137CDSSimon J.D.Li T.S.Erkal D.Pace A.B.Drlica-Wagner A.James D.J.,Marshall J.L.Bechtol K.Hansen T.Kuehn K.Lidman C.Allam S.,Annis J.Avila S.Bertin E.Brooks D.Burke D.L.Carnero Rosell A.,Carrasco Kind M.Carretero J.da Costa L.N.De Vicente J.Desai S.,Doel P.Eifler T.F.Everett S.Fosalba P.Frieman J.Garcia-Bellido J.,Gaztanaga E.Gerdes D.W.Gruen D.Gruendl R.A.Gschwend J.,Gutierrez G.Hollowood D.L.Honscheid K.Krause E.Kuropatkin N.,MacCrann N.Maia M.A.G.March M.Miquel R.Palmese A.Paz-Chinchon F.,Plazas A.A.Reil K.Roodman A.Sanchez E.Santiago B.Scarpine V.,Schubnell M.Serrano S.Smith M.Suchyta E.Tarle G.Walker A.R.(The DES Collaboration)2023-02-17T16:01:43Z2021-09-16T11:49:21ZCDS support team

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

cds-question@unistra.frgalaxiesspectroscopyradial-velocityline-intensitiesmetallicityinfrared-photometryvisible-astronomyphotometryWe present Magellan/IMACS spectroscopy of three recently discovered ultra-faint Milky Way satellites, Grus II, Tucana IV, and Tucana V. We measure systemic velocities of v_hel_=-110.0+/-0.5km/s, v_hel_=15.9_-1.7_^+1.8^km/s, and v_hel_=-36.2_-2.2_^+2.5^km/s for the three objects, respectively. Their large relative velocities demonstrate that the satellites are unrelated despite their close physical proximity. We determine a velocity dispersion for Tuc IV of {sigma}=4.3_-1.0_^+1.7^km/s, but we cannot resolve the velocity dispersions of the other two systems. For Gru II, we place an upper limit (90% confidence) on the dispersion of {sigma}<1.9km/s, and for Tuc V, we do not obtain any useful limits. All three satellites have metallicities below [Fe/H]=-2.1, but none has a detectable metallicity spread. We determine proper motions for each satellite based on Gaia astrometry and compute their orbits around the Milky Way. Gru II is on a tightly bound orbit with a pericenter of 25_-7_^+6^kpc and orbital eccentricity of 0.45_-0.05_^+0.08^. Tuc V likely has an apocenter beyond 100kpc and could be approaching the Milky Way for the first time. The current orbit of Tuc IV is similar to that of Gru II, with a pericenter of 25_-8_^+11^kpc and an eccentricity of 0.36_-0.06_^+0.13^. However, a backward integration of the position of Tuc IV demonstrates that it collided with the Large Magellanic Cloud at an impact parameter of 4kpc ~120Myr ago, deflecting its trajectory and possibly altering its internal kinematics. Based on their sizes, masses, and metallicities, we classify Gru II and Tuc IV as likely dwarf galaxies, but the nature of Tuc V remains uncertain.2020ApJ...892..137Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/892/137CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/357 : The Dark Energy Survey (DES): Data Release 1 (Abbott+, 2018)I/345 : Gaia DR2 (Gaia Collaboration, 2018)J/AJ/131/2514 : Radial velocities of red giants in the SMC (Harris+, 2006)J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)J/MNRAS/434/1681 : Extremely metal-poor stars CaII triplet (Carrera+, 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/780/59 : The Araucaria project: EBs in SMC (Graczyk+, 2014)J/ApJ/808/95 : Spectroscopy of Reticulum II (Simon+, 2015)J/MNRAS/458/L59 : Draco II stars gi mag & radial velocities (Martin+, 2016)J/ApJ/819/53 : Magellan/M2FS spec. of Tucana 2 & Grus 1 (Walker+, 2016)J/ApJ/838/83 : Rvel, abundances & membership in TriII (Kirby+, 2017)J/ApJ/838/11 : Member stars in the MW satellite Tucana III (Simon+, 2017)J/ApJ/866/22 : Spectroscopic analysis of Tuc III stream (Li+, 2018)J/ApJ/857/145 : MagLiteS Carina II and Carina III spectroscopy (Li+, 2018)J/A+A/620/A155 : Gaia proper motions of 7 UFD galaxies (Massari+, 2018)J/ApJ/863/89 : Gaia PMs of stars in ultra-faint MW satellites (Simon, 2018)J/AJ/156/257 : Spec. of RGB stars in Draco & Ursa Minor (Spencer+, 2018)J/MNRAS/482/5138 : Galactic GC mean PMs & velocities (Baumgardt+, 2019)J/ApJ/883/11 : Magellan/IMACS spectra of Crater II & Hercules (Fu+, 2019)J/ApJ/870/83 : Abund. in ultra-faint dwarf gal. GruI & TriII (Ji+, 2019)J/ApJ/885/53 : Spectrosc. & HST phot. of galaxy Leo V (Mutlu-Pakdil+, 2019)J/ApJ/875/77 : PMs of MW satellites with Gaia & DES (Pace+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/892/137https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/892/137http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/892/137https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/892/137https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/892/137http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/892/137GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/892/137/table3 (Magellan/Baade IMACS velocity and metallicity measurements for Gru II, Tuc IV, and Tuc V)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/892/137/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/892/137/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/892/137/table3?GETtext/xml+votable180.050000true330.73088-46.427470.005555555555555556Cone search capability for table J/ApJ/892/137/table2 (*Anglo-Australian Telescope (AAT) velocity measurements for Gru II and Tuc IV)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/892/137/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/892/137/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/892/137/table2?GETtext/xml+votable180.050000true329.61985-46.558230.0055555555555555565/11655 6/34850-34851 34856-34858 34944 46089 46092 46100-46101 46144 46615 46658 46664 46666https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/892/137?format=asciiOpticalInfrareddefaultJ/ApJ/892/137/table3Magellan/Baade IMACS velocity and metallicity measurements for Gru II, Tuc IV, and Tuc V[Fe/H][-3.4/-1.5]? Metallicitylog(Sun)phys.abund.Zfloatnullablee_[Fe/H][0.16/0.9]? Uncertainty in [Fe/H]log(Sun)stat.error;phys.abund.FefloatnullableMm[0/1] Membership code (1)meta.code.memberintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGalGalaxy satellite ("GruII", "TucIV" or "TucV"); column added by CDSsrc.class.starGalaxy;instr.obstycharDESIdentifier (JHHMMSS.ss+DDMMSS.s)meta.id;meta.maincharNrvNumber of HRV measurements for this DES sourcemeta.numberintnullableRAJ2000Right Ascension (J2000)degpos.eq.ra;meta.mainSimbadSimbad column added by the CDSmeta.ref.urlcharDEJ2000[-63.34/-46.2] Declination (J2000)degpos.eq.dec;meta.maingmag[16.7/22] DES dereddened g band (AB) magnitude (G1)magphot.mag;em.opt.Bfloatrmag[15.78/21.3] DES dereddened r band (Ab) magnitude (G1)magphot.mag;em.opt.RfloatMJD[57247.4/58363.8] Modified Julian Datedtime.epochfloatS/N[4/162] Signal to noise ratiostat.snrfloatHRV[-227/349] Heliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloate_HRV[1/9.6] Uncertainty in HRVkm/sstat.errorfloatEW[0.4/8.3]? Ca triplet equivalent width0.1nmspect.line.eqWidthfloatnullablee_EW[0.3/2]? Uncertainty in EW0.1nmstat.error;spect.line.eqWidthfloatnullableJ/ApJ/892/137/table2*Anglo-Australian Telescope (AAT) velocity measurements for Gru II and Tuc IVrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDESIdentifier (JHHMMSS.ss+DDMMSS.s)meta.id;meta.maincharrmag[15.25/18.7] DES dereddened r band (AB) magnitude (G1)magphot.mag;em.opt.RfloatSimbadSimbad column added by the CDSmeta.ref.urlcharMJD[57596.1/57596.6] Modified Julian Datedtime.epochfloatRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.maingmag[16.2/19.25] DES dereddened g band (AB) magnitude (G1)magphot.mag;em.opt.BfloatS/N[6/42] Signal to noise ratiostat.snrfloatHRV[-164/258] Heliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloate_HRV[0.7/24.2] Uncertainty in HRVkm/sstat.errorfloat