J/A+A/655/A117ivo://CDS.VizieR/J/A+A/655/A117doi:10.26093/cds/vizier.36550117CDSBensby T.Gould A.Asplund M.Feltzing S.Melendez J.Johnson J.A.,Lucatello S.Udalski A.Yee J.C.2022-10-10T15:06:47Z2021-12-01T09:15:37ZCDS support team

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

cds-question@unistra.frmilky-way-galaxyg-starschemical-abundancesradio-astronomyNext to H and He, carbon is, together with oxygen, the most abundant element in the Universe and widely used when modelling the formation and evolution of galaxies and their stellar populations. For the Milky Way bulge, there are currently essentially no measurements of carbon in un-evolved stars, hampering our abilities to properly compare Galactic chemical evolution models to observational data for this still enigmatic stellar population. We aim to determine carbon abundances for our sample of 91 microlensed dwarf and subgiant stars in the Galactic bulge. Together with new determinations for oxygen this forms the first statistically significant sample of bulge stars that have C and O abundances measured, and for which the C abundances have not been altered by the nuclear burning processes internal to the stars. Our analysis is based on high-resolution spectra for a sample of 91 dwarf and subgiant stars that were obtained during microlensing events when the brightnesses of the stars were highly magnified. Carbon abundances were determined through spectral line synthesis of six CI lines around 9100{AA}, and oxygen abundances using the three OI lines at about 7770{AA}. One-dimensional (1D) MARCS model stellar atmospheres calculated under the assumption of local thermodynamic equilibrium (LTE) were used, and non-LTE corrections were applied when calculating the synthetic spectra for both C and O. Carbon abundances was possible to determine for 70 of the 91 stars in the sample and oxygen abundances for 88 of the 91 stars in the sample. The [C/Fe] ratio evolves essentially in lockstep with [Fe/H], centred around solar values at all [Fe/H]. The [O/Fe]-[Fe/H] trend has an appearance very similar to that observed for other alpha-elements in the bulge, with the exception of a continued decrease in [O/Fe] at super-solar [Fe/H], where other alpha-elements tend to level out. When dividing the bulge sample into two sub-groups, one younger than 8Gyr and one older than 8Gyr, the stars in the two groups follow exactly the elemental abundance trends defined by the solar neighbourhood thin and thick disks, respectively. Comparisons with recent models of Galactic chemical evolution in the [C/O]-[O/H] plane show that the models that best match the data are the ones that have been calculated with the Galactic thin and thick disks in mind. We conclude that carbon, oxygen, and the combination of the two support the idea that the majority of the stars in the Galactic bulge have a secular origin; that is, they are formed from disk material. We cannot exclude that a fraction of stars in the bulge could be classified as a classical bulge population, but it would have to be small. More dedicated and advanced models of the inner region of the Milky Way are needed to make more detailed comparisons to the observations.2021A&A...655A.117Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/655/A117CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/605/A89 : Abundances of microlensed bulge stars (Bensby+, 2017)J/A+A/634/A130 : Lithium abundances in microlensed dwarf stars (Bensby+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/655/A117https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/655/A117http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/655/A117https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/655/A117https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/655/A117http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/655/A117GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/655/A117/table2 (C and O abundances and uncertainties.)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/655/A117/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/655/A117/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/655/A117/table2?GETtext/xml+votable180.050000true270.5320833-31.4240.0055555555555555565/7194 7205 7216-7217 7220 6/28711 28715 28717-28718 28723 28726 28729 28731 28733-28735 28770 28780 28782-28783 28794 28804 28817 28839 28857 28872-28873 28884 28888 29184https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/655/A117?format=asciiRadiodefaultJ/A+A/655/A117/table2C and O abundances and uncertainties.recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName of microlensing source starmeta.id;meta.maincharNumInternal numbering of starmeta.idint[C/H]? [C/H] abundance normalised to Sunphys.abundfloatnullable[O/H]? [O/H] abundance normalised to Sunphys.abundfloatnullablee_[C/H]? Error on [C/H]stat.error;phys.abundfloatnullablee_[O/H]? Error on [O/H]stat.error;phys.abundfloatnullablee_[C/O]? Error on [C/O]stat.error;phys.abundfloatnullablee_[C/Fe]? Error on [C/Fe]stat.error;phys.abundfloatnullablee_[O/Fe]? Error on [O/Fe]stat.error;phys.abundfloatnullableAO7772? Absolute abundance for O 7772 linephys.abundfloatnullableAO7774? Absolute abundance for O 7774 linephys.abundfloatnullableAO7775? Absolute abundance for O 7775 linephys.abundfloatnullableAC9061? Absolute abundance for C 9061 linephys.abundfloatnullableAC9063? Absolute abundance for C 9063 linephys.abundfloatnullableAC9078? Absolute abundance for C 9078 linephys.abundfloatnullableAC9089? Absolute abundance for C 9089 linephys.abundfloatnullableAC9094? Absolute abundance for C 9094 linephys.abundfloatnullableAC9111? Absolute abundance for C 9111 linephys.abundfloatnullableFlag1[0/2]? Flag on C 9061 line (1)meta.code.errorintnullableFlag2[0/2]? Flag on C 9063 line (1)meta.code.errorintnullableFlag3[0/2]? Flag on C 9078 line (1)meta.code.errorintnullableFlag4[0/2]? Flag on C 9089 line (1)meta.code.errorintnullableFlag5[0/2]? Flag on C 9094 line (1)meta.code.errorintnullableSimbadNameSimbad column added by the CDSmeta.idcharnullableFlag6[0/2]? Flag on C 9111 line (1)meta.code.errorintnullable_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main