J/ApJ/870/83ivo://CDS.VizieR/J/ApJ/870/83doi:10.26093/cds/vizier.18700083CDSJi A.P.Simon J.D.Frebel A.Venn K.A.Hansen T.T.2021-09-07T11:20:51Z2020-07-24T14:34:24ZCDS support team

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

cds-question@unistra.frchemical-abundancesline-intensitiesvisible-astronomyspectroscopyradial-velocityWe present high-resolution spectroscopy of four stars in two candidate ultra-faint dwarf galaxies (UFDs), GrusI (GruI) and TriangulumII (TriII). Neither object currently has a clearly determined velocity dispersion, placing them in an ambiguous region of parameter space between dwarf galaxies and globular clusters (GCs). No significant metallicity difference is found for the two GruI stars, but both stars are deficient in neutron-capture elements. We verify previous results that TriII displays significant spreads in metallicity and [{alpha}/Fe]. Neutron-capture elements are not detected in our TriII data, but we place upper limits at the lower envelope of Galactic halo stars, consistent with previous very low detections. Stars with similarly low neutron-capture element abundances are common in UFDs but rare in other environments. This signature of low neutron-capture element abundances traces chemical enrichment in the least massive star-forming dark matter halos and further shows that the dominant sources of neutron-capture elements in metal-poor stars are rare. In contrast, all known GCs have similar ratios of neutron-capture elements to those of halo stars, suggesting that GCs do not form at the centers of their own dark matter halos. The low neutron-capture element abundances may be the strongest evidence that GruI and TriII are (or once were) galaxies rather than GCs, and we expect future observations of these systems to robustly find nonzero velocity dispersions or signs of tidal disruption. However, the nucleosynthetic origin of this low neutron-capture element floor remains unknown.2019ApJ...870...83Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/870/83CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/128/1177 : Galactic stellar abundances (Venn+, 2004)J/AJ/130/2140 : Abundances and velocities in globular clusters (Pritzl+, 2005)J/AJ/137/3100 : Radial velocities of 4 dSph galaxies (Walker+, 2009)J/AN/331/474 : Abundances of metal-poor stars (Frebel, 2010)J/ApJ/711/573 : Detailed abundances in a halo stellar stream (Roederer+, 2010)J/ApJ/724/341 : Nucleosynthesis of massive metal-free stars (Heger+, 2010)J/ApJ/767/134 : Abundances of red giant stars in UFD galaxies (Vargas+, 2013)J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 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/AJ/145/159 : LAMOST. II. ugriz photometry of 526 new quasars (Huo+, 2013)J/A+A/562/A146 : Chemical abundances of 8 metal-poor stars (Ishigaki+, 2014)J/A+A/565/A23 : Abundances of NGC5897 red giants (Koch+, 2014)J/A+A/571/A47 : Extensive list of CH in stellar atmospheres (Masseron+, 2014)J/AJ/147/136 : Stars very low metal abundance. VI. Abundances (Roederer+,2014)J/ApJ/786/74 : EW measurements of 6 Segue 1 red giants (Frebel+, 2014)J/ApJ/789/147 : Star formation histories of LG dwarf galaxies (Weisz+, 2014)J/ApJ/797/21 : Carbon-enhanced metal-poor stars (Placco+, 2014)J/A+A/574/A129 : The First CEMP star in the Sculptor dSph (Skuladottir+,2015)J/ApJ/802/93 : Chemical abundance analysis 5 stars in Sculptor (Simon+, 2015)J/ApJ/808/95 : Spectroscopy of Reticulum II (Simon+, 2015)J/MNRAS/449/761 : EWs of metal-poor stars in UMiI dSph galaxy (Ural+, 2015)J/MNRAS/449/3889 : Detailed abundances of 15 stars in NGC4833 (Roederer+, 2015)J/AJ/151/82 : The 4 brightest red giants in UFD galaxy Ret 2 (Roederer+,2016)J/ApJ/817/41 : Abundances of 4 metal-poor red giants in BooII (Ji+, 2016)J/ApJ/819/53 : Magellan/M2FS spectroscopy of Tucana 2 & Grus 1 (Walker+, 2016)J/ApJ/826/110 : Boo-127 and Boo-980 high-resolution spectra (Frebel+, 2016)J/ApJ/830/93 : Abundances of Ret II brightest red giant members (Ji+, 2016)J/MNRAS/458/L59 : DracoII stars gi magnitude & radial velocities (Martin+,2016)J/A+A/604/A129 : Formation of MW halo and dwarf satellites (Mashonkina+, 2017)J/ApJ/838/11 : Member stars in the MW satellite Tucana III (Simon+, 2017)J/ApJ/838/44 : Abundances of the brightest member of Tuc III (Hansen+, 2017)J/ApJ/838/83 : Radial velocities abundances membership in TriII (Kirby+, 2017)J/ApJS/230/28 : The populations of Carina. II. Abundances (Norris+, 2017)J/ApJ/852/99 : Abundances 3 metal-poor stars in Horologium I (Nagasawa+, 2018)J/ApJ/855/83 : Abundances very metal-poor stars in Sagittarius (Hansen+, 2018)J/ApJ/857/74 : Abundances of 7 new member stars in Tucana II (Chiti+, 2018)J/ApJ/863/89 : GaiaDR2 PMs of stars in ultra-faint MW satellites (Simon, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/870/83https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/870/83http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/870/83https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/870/83https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/870/83http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/870/83GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/870/83/table1 (Observing details of the four stars in the ultra-faint dwarf galaxies (UFDs) GruI and TriII)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/870/83/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/870/83/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/870/83/table1?GETtext/xml+votable180.050000true344.242083-50.232750.0055555555555555566/2352 46279 46290https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/870/83?format=asciiOpticaldefaultJ/ApJ/870/83/table1Observing details of the four stars in the ultra-faint dwarf galaxies (UFDs) GruI and TriIISimbadNameSimbad column added by the CDSmeta.idcharInstSpectrograph usedmeta.id;instrcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqStar number (as in Table 2); column added by CDSmeta.id;meta.mainintNameStar identificationmeta.idcharRAJ2000[2/22] Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of declination (J2000)pos.eq.dec;meta.mainVmag[17/19] V magnitudemagphot.mag;em.opt.VfloatDateObservation datetime.epoch;obsnullableExp[60/430] Exposure timemintime.duration;obs.exposureintHRV[-397/-139] Helicocentric velocity (1)km/sspect.dopplerVelocfloate_HRV[0.4/5]? Error on RVkm/sstat.errorfloatnullableS/N4500[1/22]? Signal-to-noise ratio at 4500{AA} per pixel (2)stat.snrintnullableS/N5300[7/25]? Signal-to-noise ratio at 5300{AA} per pixel (2)stat.snrintnullableS/N6500[17/60]? Signal-to-noise ratio at 6500{AA} per pixel (2)stat.snrintnullableEWsDisplay the equivalent width measurements for this star (link to Table 2)meta.ref.urlcharJ/ApJ/870/83/table2Line measurementsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIonAtomic speciesphys.atmol.ionStagecharlambda[3961/8195] Rest wavelength ({lambda})0.1nmem.wlfloatEP[0/4.5]? Excitation potential ({chi})eVphys.atmol.excitationfloatnullableloggf[-5.7/0.65]? log statistical weight*oscillator strengthstat.weight;phys.atmol.oscStrengthfloatnullableEW1[22/311]? Measured equivalent width, GruI-0320.1pmspect.line.eqWidthfloatnullablef_EW1syn: abundance from spectrum synthesismeta.codechare_EW1[5/66]? Uncertainty in EW1 ({sigma}(EW))0.1pmstat.errorfloatnullablel_logeps1Limit flag on logeps1meta.code.errorcharlogeps1[-2.5/5.7]? Abundance derived from this line, GruI-032 (log{epsilon})phys.abundfloatnullablee_logeps1[0.1/1.2]? Uncertainty on logeps1 ({sigma}(log{epsilon}))stat.errorfloatnullableEW2[20/280]? Measured equivalent width, GruI-0380.1pmspect.line.eqWidthfloatnullablef_EW2syn: abundance from spectrum synthesismeta.codechare_EW2[5/79]? Uncertainty in EW2 ({sigma}(EW))0.1pmstat.errorfloatnullablel_logeps2Limit flag on logeps2meta.code.errorcharlogeps2[-1.8/5.7]? Abundance derived from this line, GruI-038 (log{epsilon})phys.abundfloatnullablee_logeps2[0.1/1.5]? Uncertainty on logeps2 ({sigma}(log{epsilon}))stat.errorfloatnullableEW3[16/209]? Measured equivalent width, TriII-400.1pmspect.line.eqWidthfloatnullablef_EW3syn: abundance from spectrum synthesismeta.codechare_EW3[4/34]? Uncertainty in EW3 ({sigma}(EW))0.1pmstat.errorfloatnullablel_logeps3Limit flag on logeps3meta.code.errorcharlogeps3[-2.3/5.1]? Abundance derived from this line, TriII-40 (log{epsilon})phys.abundfloatnullablee_logeps3[0.1/0.5]? Uncertainty on logeps3 ({sigma}(log{epsilon}))stat.errorfloatnullableEW4[52/207]? Measured equivalent width, TriII-460.1pmspect.line.eqWidthfloatnullablef_EW4syn: abundance from spectrum synthesismeta.codechare_EW4[12/70]? Uncertainty in EW4 ({sigma}(EW))0.1pmstat.errorfloatnullablel_logeps4Limit flag on logeps4meta.code.errorcharlogeps4[-0.06/6.2]? Abundance derived from this line, TriII-46 (log{epsilon})phys.abundfloatnullablee_logeps4[0.2/1.1]? Uncertainty on logeps4 ({sigma}(log{epsilon}))stat.errorfloatnullable