J/A+A/604/A41ivo://CDS.VizieR/J/A+A/604/A41doi:10.26093/cds/vizier.36040041CDSKoch A.Hansen C.J.Kunder A.M.2017-09-04T07:59:28Z2017-08-01T06:50:19ZCDS support team

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

cds-question@unistra.frglobular-star-clustersradial-velocitychemical-abundancesGlobular clusters (GCs) have long been recognized as being amongst the oldest objects in the Galaxy. As such, they have the potential of playing a pivotal role in deciphering the Milky Way's early history. Here we present the first spectroscopic study of the low-mass system ESO452-SC11 using the AAOmega multifibre spectrograph at medium resolution. Given the stellar sparsity of this object and the high degree of foreground contamination due to its location toward the Galactic bulge, very few details are known for this cluster - there is no consensus, for instance, about its age, metallicity, or its association with the disk or bulge. We identify five member candidates based on common radial velocity, calcium-triplet metallicity, and position within the GC. Using spectral synthesis, the measurement of accurate Fe-abundances from Fe-lines, and abundances of several {alpha}-, Fe-peak, and neutron-capture elements (Si, Ca, Ti,Cr, Co, Ni, Sr, and Eu) is carried out, albeit with large uncertainties. We find that two of the five cluster candidates are likely non-members, as they have deviating iron abundances and [alpha/Fe] ratios. The cluster mean heliocentric velocity is 19+/-2km/s with a velocity dispersion of 2.8+/-3.4km/s, a low value in line with its sparse nature and low mass. The mean Fe-abundance from spectral fitting is -0.88+/-0.03dex, where the spread is driven by observational errors. Furthermore, the alpha-elements of the GC candidates are marginally lower than expected for the bulge at similar metallicities. As spectra of hundreds of stars were collected in a 2-degree field centered on ESO452-SC11, a detailed abundance study of the surrounding field was also enabled. The majority of the non-members have slightly higher [Fe] ratios, in line with the typical nearby bulge population. A subset of the spectra with measured Fe-peak abundance ratios shows a large scatter around solar values, albeit with large uncertainties. Furthermore, our study provides the first systematic measurements of strontium abundances in a Galactic bulge GC. Here, the Eu and Sr abundances of the GC candidates are broadly consistent with a disk or bulge association. Recent proper motions and our orbital calculations place ESO452 on an elliptical orbit in the central 3kpc of the Milky Way, establishing a firm connection with the bulge. Finally, while the radial velocities and preferential position of a dozen of stars outside the GC radius appear to imply the presence of extra-tidal stars, their significantly different chemical composition refutes this hypothesis.2017A&A...604A..41Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/604/A41CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/604/A41https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/604/A41http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/604/A41https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/604/A41https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/604/A41http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/604/A41GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/604/A41/table2 (Properties of the target stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/604/A41/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/604/A41/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/604/A41/table2?GETtext/xml+votable180.050000true249.86625-28.4019720.0055555555555555565/10715 6/42859 42948-42949https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/604/A41?format=asciiOpticaldefaultJ/A+A/604/A41/table2Properties of the target starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNote[M] M for member candidates, else fore- and background candidatesmeta.notecharStarStar identifiermeta.id;meta.mainintprimarySampindicates stellar parameters and abundances in sample tablemeta.ref.urlcharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainrRadial distance from cluster centerarcminphys.angSizefloatHRVHeliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloate_HRVError on HRVkm/sstat.errorfloatSigmaEW? Reduced equivalent width1e-13mspect.line.eqWidthfloatnullablee_SigmaEW? Error on SigmaEW1e-13mstat.errorfloatnullable[Fe/H]CaT? Calcium triplet metallicityphys.abundfloatnullablee_[Fe/H]CaT? Error on [Fe/H]CaTstat.error;phys.abund.FefloatnullableJ/A+A/604/A41/samplestellar parameters (table 3) and abundances from SP_ACE (tables 4 and 5)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNote[M] M for member candidates, else fore- and background candidatesmeta.notecharStarStar identifiermeta.id;meta.mainintJ-K2MASS J-K color index (reddened)magphot.color;em.IR.J;em.IR.KfloatTeff(A)? Effective temperature from Alonso calibrationKphys.temperature.effectiveintnullableTeff(S)Effective temperature from SP_ACE pipelineKphys.temperature.effectiveinte_TeffLower error bound on Teff(SP_ACE)Kstat.error;phys.temperature.effectiveintE_TeffUpper error bound on Teff(SP_ACE)Kstat.error;stat.maxintloggSurvace gravitylog(cm.s**-2)phys.gravityfloate_loggLower error bound on logglog(cm.s**-2)stat.errorfloatE_loggUpper error bound on logglog(cm.s**-2)stat.error;stat.maxfloatvmicMicroturbulence velocitykm/sphys.veloc.microTurbfloatSNRSignal-t-Noise ratiostat.snr;arith.ratiointchi2Chi^2^ value of spectral fittingstat.fit.chi2float[Fe/H]? Iron abundance from SP_ACEphys.abund.Fefloatnullablee_[Fe/H]? Lower error bound on [Fe/H]stat.error;phys.abund.FefloatnullableE_[Fe/H]? Upper error bound on [Fe/H]stat.error;stat.maxfloatnullablenFeNumber of Fe linesmeta.numberint[Si/Fe]? [Si/Fe] abundance ratio from SP_ACEphys.abund;arith.ratiofloatnullablee_[Si/Fe]? Lower error bound on [Si/Fe]stat.error;phys.abundfloatnullableE_[Si/Fe]? Upper error bound on [Si/Fe]stat.error;stat.maxfloatnullablenSiNumber of Si linesmeta.numberint[Ca/Fe]? [Ca/Fe] abundance ratio from SP_ACEphys.abund;arith.ratiofloatnullablee_[Ca/Fe]? Lower error bound on [Ca/Fe]stat.error;phys.abundfloatnullableE_[Ca/Fe]? Upper error bound on [Ca/Fe]stat.error;stat.maxfloatnullablenCaNumber of Ca linesmeta.numberint[Ti/Fe]? [Ti/Fe] abundance ratio from SP_ACEphys.abund;arith.ratiofloatnullablee_[Ti/Fe]? Lower error bound on [Ti/Fe]stat.error;phys.abundfloatnullableE_[Ti/Fe]? Upper error bound on [Ti/Fe]stat.error;stat.maxfloatnullablenTiNumber of Ti linesmeta.numberint[Cr/Fe]? [Cr/Fe] abundance ratio from SP_ACEphys.abund;arith.ratiofloatnullablee_[Cr/Fe]? Lower error bound on [Cr/Fe]stat.error;phys.abundfloatnullableE_[Cr/Fe]? Upper error bound on [Cr/Fe]stat.error;stat.maxfloatnullablenCrNumber of Cr linesmeta.numberint[Co/Fe]? [Co/Fe] abundance ratio from SP_ACEphys.abund;arith.ratiofloatnullablee_[Co/Fe]? Lower error bound on [Co/Fe]stat.error;phys.abundfloatnullableE_[Co/Fe]? Upper error bound on [Co/Fe]stat.error;stat.maxfloatnullablenCoNumber of Co linesmeta.numberint[Ni/Fe]? [Ni/Fe] abundance ratio from SP_ACEphys.abund;arith.ratiofloatnullablee_[Ni/Fe]? Lower error bound on [Ni/Fe]stat.error;phys.abundfloatnullableE_[Ni/Fe]? Upper error bound on [Ni/Fe]stat.error;stat.maxfloatnullablenNiFeNumber of Ni linesmeta.numberint[Sr/Fe]? [Sr/Fe] abundance ratio from SP_ACEphys.abund;arith.ratiofloatnullablee_[Sr/Fe]? Error on [Sr/Fe]stat.error;phys.abundfloatnullablel_[Eu/Fe]Limit flag on [Eu/Fe]meta.code.error;phys.abundchar[Eu/Fe]? [Sr/Fe] abundance ratio from SP_ACEphys.abund;arith.ratiofloatnullablee_[Eu/Fe]? Error on [Eu/Fe]stat.error;phys.abundfloatnullable