Heavy elements in galactic bulge stars

Abstract

The aim is to obtain abundance ratios in individual stars of the Galactic bulge, including field and globular duster stars, in order to identify them to different stellar populations, and different bulge formation scenarios. Jhe sample consists of 800 bulge stars, with spectra obtained with the FLAMES spectrograph, including 55 stars observed with the UVES spectrograph, at a resolution of 55,000, and 800 stars observed with the GIRAFFE spectrograph, at a resolution of 22,000. The observations were earned out in 4 fields: Baade's Window (1=1.14º, b=4.2º), field at -6º (1=0.2º, b=06º), Blanco field (I=0o, b=-12º), and field near NGC 6553 (I=5.2º, b=-3º). The abundance determination will be performed through calculations of synthetic spectra, using the codes turbospectrum and pfant06. The elements to be analyzed are formed by neutron-capture, both in the s-process and the r-process This includes the elements Ytrium, Strontium, Zirconium, Lantanum, Barium, formed dominantly in the s-process, and Europium, formed dominantly in the r-process. Spedal attention will be given to metal-poor stars, with metallicities around [Fe/H]~-1.0, in order to verify if they show excesses of s-elements, similarly to the globular duster NGC 6522, as found Chiappini et at. (2011). The final objective is to understand the processes of bulge formation, and to know the characteristics of the first supemovae that enriched the Galactic bulge at early times. (AU)