J/A+A/527/A18ivo://CDS.VizieR/J/A+A/527/A18doi:10.26093/cds/vizier.35270018CDSPancino E.Mucciarelli A.Sbordone L.Bellazzini M.Monaco L.,Ferraro F.R.2018-02-02T10:34:12Z2011-01-20T07:49:15ZCDS support team

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

cds-question@unistra.frglobular-star-clustersgiant-starspopulation-ii-starsline-intensitiesWe analysed high-resolution UVES spectra of six stars belonging to the subgiant branch of {omega} Centauri, and derived abundance ratios of 19 chemical elements (namely Al, Ba, C, Ca, Co, Cr, Cu, Fe, La, Mg, Mn, N, Na, Ni, Sc, Si, Sr, Ti, and Y). A comparison with previous abundance determinations for red giants provided remarkable agreement and allowed us to identify the sub-populations to which our targets belong. We found that three targets belong to a low-metallicity population at [Fe/H]=-2.0dex, [alpha/Fe]=+0.4dex and [s/Fe]=0dex. Stars with similar characteristics were found in small amounts by past surveys of red giants. We discuss the possibility that they belong to a separate sub-population that we name VMP (very metal-poor, at most 5% of the total cluster population), which - in the self-enrichment hypothesis - is the best-candidate first stellar generation in {omega} Cen. Two of the remaining targets belong to the dominant metal-poor population (MP) at [Fe/H]=-1.7dex, and the last one to the metal-intermediate (MInt) one at [Fe/H]=-1.2dex. The existence of the newly defined VMP population could help to understand some puzzling results based on low-resolution spectroscopy (Sollima et al. 2005ApJ...634..332S , Villanova et al., 2007, Cat. J/ApJ/663/296) in their age differences determinations, because the metallicity resolution of these studies was probably not enough to detect the VMP population. The VMP could also correspond to some of the additional substructures of the subgiant-branch region found in the latest HST photometry (Bellini et al., 2010, Cat. J/AJ/140/631). After trying to correlate chemical abundances with substructures in the subgiant branch of {omega} Cen, we found that the age difference between the VMP and MP populations should be small (0+/-2Gyr), while the difference between the MP and MInt populations could be slightly larger (2+/-2Gyr).2011A&A...527A..18Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/527/A18CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/663/296 : omega Cen (NGC5139) subgiants UBV(RI)c phot. (Villanova+, 2007)J/AJ/135/1395 : omega Cen Spitzer photometry (Boyer+, 2008)J/A+A/493/959 : UBV(RI)cHalpha photometry in omega Cen (Bellini+, 2009)J/AJ/140/631 : HST WFC3/UVIS photometry of omega Cen core (Bellini+, 2010)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/527/A18https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/527/A18http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/527/A18https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/527/A18https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/527/A18http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/527/A18GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/527/A18/table1 (Observing logs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/527/A18/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/527/A18/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/527/A18/table1?GETtext/xml+votable180.050000true201.96008611-47.759426110.0055555555555555566/432253.322582951404819e-19 3.852589004194616e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/527/A18?format=asciiOpticaldefaultJ/A+A/527/A18/table1Observing logsNotesNotesmeta.notecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintWFIWFI identification number of subgiantmeta.id;meta.mainintRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainVmagV magnitudemagphot.mag;em.opt.Vfloat(B-V)0Deredenned B-V colour indexmagphot.color;em.opt.B;em.opt.Vfloat(V-I)0Deredenned V-I colour indexmagphot.color;em.opt.V;em.opt.IfloatRResolution ({lambda}/{dlta}{lambda} ratio)spect.resolutionintTexpExposure timestime.duration;obs.exposureintS/NSignal-to-noise ratio at 550nmstat.snrintRVRadial velocitykm/sphys.veloc;pos.heliocentricfloate_RVrms uncertainty on RVkm/sstat.errorfloatJ/A+A/527/A18/table2Equivalent widths and atomic datarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength in Angstroms0.1nmem.wlfloatIonElement name and ionization stagemeta.id;phys.atmol.ionStage;phys.atmol.ionizationcharEPExcitation potentialeVphys.atmol.excitationfloatloggfLogarithm of the oscillator strengthphys.atmol.oscStrengthfloatW503358? Equivalent width of star WFI 503358 (1)0.1pmspect.line.eqWidthfloatnullablee_W503358? formal error on W503358 (in m{AA}) (1)0.1pmstat.errorfloatnullableq_W503358? DAOSPEC Q parameter for star WFI 503358 (1)meta.code.qualfloatnullableW503951? Equivalent width of star WFI 503951 (1)0.1pmspect.line.eqWidthfloatnullablee_W503951? formal error on W503951 (in m{AA}) (1)0.1pmstat.errorfloatnullableq_W503951? DAOSPEC Q parameter for star WFI 503951 (1)meta.code.qualfloatnullableW507109? Equivalent width of star WFI 507109 (1)0.1pmspect.line.eqWidthfloatnullablee_W507109? formal error on W507109 (in m{AA}) (1)0.1pmstat.errorfloatnullableq_W507109? DAOSPEC Q parameter for star WFI 507109 (1)meta.code.qualfloatnullableW507633? Equivalent width of star WFI 507633 (1)0.1pmspect.line.eqWidthfloatnullablee_W507633? formal error on W507633 (in m{AA}) (1)0.1pmstat.errorfloatnullableq_W507633? DAOSPEC Q parameter for star WFI 507633 (1)meta.code.qualfloatnullableW512115? Equivalent width of star WFI 512115 (1)0.1pmspect.line.eqWidthfloatnullablee_W512115? formal error on W512115 (in m{AA}) (1)0.1pmstat.errorfloatnullableq_W512115? DAOSPEC Q parameter for star WFI 512115 (1)meta.code.qualfloatnullableW512938? Equivalent width of star WFI 512938 (1)0.1pmspect.line.eqWidthfloatnullablee_W512938? formal error on W512938 (in m{AA}) (1)0.1pmstat.errorfloatnullableq_W512938? DAOSPEC Q parameter for star WFI 512938 (1)meta.code.qualfloatnullable