J/A+A/577/A18ivo://CDS.VizieR/J/A+A/577/A18doi:10.26093/cds/vizier.35770018CDSKacharov N.Koch A.Caffau E.Sbordone L.2017-12-12T14:45:20Z2015-04-24T07:20:38ZCDS support team

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

cds-question@unistra.frglobular-star-clustersmilky-way-galaxyinfrared-astronomyspectroscopychemical-abundancesSulphur is an important, volatile alpha element but its role in the Galactic chemical evolution is still uncertain. We derive the S abundances in RGB stars in three Galactic globular clusters (GC) that cover a wide metallicity range (-2.3<[Fe/H]<-1.2): M4, M22, and M30. The halo field stars show a large scatter in the [S/Fe] ratio in this metallicity span, which is inconsistent with canonical chemical evolution models. To date, very few measurements of [S/Fe] exist for stars in GCs, which are good tracers of the chemical enrichment of their environment. However, some light and alpha elements show star-to-star variations within individual GCs and it is yet unclear whether sulphur also varies between GC stars. We used the the infrared spectrograph CRIRES to obtain high-resolution (R~50000), high signal-to-noise (SNR~200 per px) spectra in the region of the SI multiplet 3 at 1045nm for 15 GC stars selected from the literature (6 stars in M4, 6 stars in M22 and 3 stars in M30). Multiplet 3 is better suited for S abundance derivation than the more commonly used lines of multiplet 1 at 920nm, since its lines are not blended by telluric absorption or other stellar features at low metallicity. We used spectral synthesis to derive the [S/Fe] ratio of the stars assuming local thermodynamic equilibrium (LTE). We find mean [S/Fe]=0.58+/-0.01+/-0.20dex (statistical and systematic error) for M4, [S/Fe]=0.57+/-0.01+/-0.19dex for M22, and [S/Fe]=0.55+/-0.02+/-0.16dex for M30. The negative NLTE corrections are estimated to be in the order of the systematic uncertainties. With the tentative exception of two stars with measured high S abundances, we conclude that sulphur behaves like a typical alpha element in the studied Galactic GCs, showing enhanced abundances with respect to the solar value at metallicities below [Fe/H]=-1.0dex without a considerable spread.2015A&A...577A..18Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/577/A18CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/490/625 : Abundances of NGC 6121 red giants (Marino+, 2008)J/A+A/505/139 : Red giants abundances in 17 globular clusters (Carretta+, 2009)J/A+A/505/117 : Red giants abundances in 15 globular clusters (Carretta+, 2009)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/577/A18https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/577/A18http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/577/A18https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/577/A18https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/577/A18http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/577/A18GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/577/A18/table1 (Atmospheric parameters and [S/Fe] ratios of the targeted stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/577/A18/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/577/A18/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/577/A18/table1?GETtext/xml+votable180.050000true245.8100739-26.60153690.0055555555555555566/28967 28972-28973 42955 48434https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/577/A18?format=asciiInfrareddefaultJ/A+A/577/A18/table1Atmospheric parameters and [S/Fe] ratios of the targeted starsSNameSimbad namemeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClusterGlobular cluster name (1)meta.id.parentcharIDStar identification number within the clustermeta.idintTeff[3860/4500] Effective temperatureKphys.temperature.effectiveintlogg[0.05/1.67] Surface gravitylog(cm.s**-2)phys.gravityfloatvtmic[1.5/2.4] Microturbulent velocity {xi}km/sphys.velocfloat[Fe/H][-2.4/-1] Metallicitylog(Sun)phys.abund.Zfloat[Na/Fe][-0.2/0.8] Na abundancelog(Sun)phys.abundfloate_[Na/Fe][0.02/0.07] rms uncertainty on [Na/Fe]log(Sun)stat.error;phys.abundfloat[O/Fe][-0.3/0.51] O abundancelog(Sun)phys.abundfloate_[O/Fe][0.04/0.2] rms uncertainty on [O/Fe]log(Sun)stat.error;phys.abundfloat[Mg/Fe][0.2/0.55]? Mg abundancelog(Sun)phys.abundfloatnullablee_[Mg/Fe][0.04/0.2]? rms uncertainty on [Mg/Fe]log(Sun)stat.error;phys.abundfloatnullable[Ca/Fe][0.16/0.42]? Ca abundancelog(Sun)phys.abundfloatnullablee_[Ca/Fe][0.02/0.03]? rms uncertainty on [Ca/Fe]log(Sun)stat.error;phys.abundfloatnullableVtmac[4.8/12.2] Macroturbulent velocity (2)km/sphys.velocfloate_Vtmac[0.1/0.9] rms uncertainty on Vtmackm/sstat.errorfloat[S/Fe][0.5/0.9] LTE S abundance (3)log(Sun)phys.abundfloate_[S/Fe][0.01/0.04] rms uncertainty on [S/Fe]log(Sun)stat.error;phys.abundfloatspSimbad column added by the CDSmeta.ref.urlcharFileNameName of the table with spectrum in subdirectory spmeta.id;meta.tablechar_RAPositions from the cited references (with fixed IDs for 2 M22 stars) (right ascension part)degpos.eq.ra;meta.main_DEPositions from the cited references (with fixed IDs for 2 M22 stars) (declination part)degpos.eq.dec;meta.main