Examinando por Autor "Barbuy, B"
Mostrando 1 - 2 de 2
Resultados por página
Opciones de ordenación
Ítem A MUSE study of the inner bulge globular cluster Terzan 9: A fossil record in the Galaxy(2019-12) Ernandes, H.; Dias, B.; Barbuy, B; Kamann, S.; Ortolani, S.; Cantelli, E; Bica, E.; Rossi, L; Ortolani, S; Cantelli, E.; Bica, E; Rossi, LContext. Moderately metal-poor inner bulge globular clusters are relics of a generation of long-lived stars that formed in the early Galaxy. Terzan 9, projected at 4°.12 from the Galactic center, is among the most central globular clusters in the Milky Way, showing an orbit which remains confined to the inner 1 kpc. Aims. Our aim is the derivation of the cluster's metallicity, together with an accurate measurement of the mean radial velocity. In the literature, metallicities in the range between-2.0 < [Fe/H] < -1.0 have been estimated for Terzan 9 based on color-magnitude diagrams and CaII triplet (CaT) lines. Methods. Given its compactness, Terzan 9 was observed using the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope. The extraction of spectra from several hundreds of individual stars allowed us to derive their radial velocities, metallicities, and [Mg/Fe]. The spectra obtained with MUSE were analysed through full spectrum fitting using the ETOILE code. Results. We obtained a mean metallicity of [Fe/H] ≈ -1.10 ±0.15, a heliocentric radial velocity of vhr = 58.1 ± 1.1 km s-1, and a magnesium-To-iron [Mg/Fe] = 0.27 ± 0.03. The metallicity-derived character of Terzan 9 sets it among the family of the moderately metal-poor Blue Horizontal Branch clusters HP 1, NGC 6558, and NGC 6522. © ESO 2019.Ítem Heavy elements Ba, La, Ce, Nd, and Eu in 56 Galactic bulge red giants(EDP SCIENCES, 2016-02) Van der Swaelmen, M; Barbuy, B; Hill, V; Zoccali, M; Minniti, D; Ortolani, S; Gomez, AAims. The aim of this work is the study of abundances of the heavy elements Ba, La, Ce, Nd, and Eu in 56 bulge giants (red giant branch and red clump) with metallicities ranging from 1 : 3 dex to 0 : 5 dex. Methods. We obtained high-resolution spectra of our giant stars using the FLAMES-UVES spectrograph on the Very Large Telescope. We inspected four bulge fields along the minor axis. Results. We measure the chemical evolution of heavy elements, as a function of metallicity, in the Galactic bulge. Conclusions. The [Ba; La; Ce; Nd = Fe] vs. [Fe = H] ratios decrease with increasing metallicity, in which aspect they differ from disc stars. In our metal-poor bulge stars, La and Ba are enhanced relative to their thick disc counterpart, while in our metal-rich bulge stars La and Ba are underabundant relative to their disc counterpart. Therefore, this contrast between bulge and discs trends indicates that bulge and (solar neighbourhood) thick disc stars could behave differently. An increase in left perpendicularLa; Nd = Euright perpendicular with increasing metallicity, for metal-rich stars with [Fe = H] > 0 dex, may indicate that the s-process from AGB stars starts to operate at a metallicity around solar. Finally, [Eu = Fe] follows the [alpha = Fe] behaviour, as expected, since these elements are produced by SNe type II.