Chemical evolution of heavy elements in the Local Group

Abstract

Only recently, the incredible progress made by telescopes in the past few years has opened the door to the detailed study of the chemical abundances in the stars belonging to the Local Group, if we exclude the solar vicinity. Thanks to this progress, the Local Group has become a natural benchmark for the chemical evolution models; the different chemical enrichments shown in the stars belonging to the different systems forming the Local Group, can be used to check the validity of the theoretical nucleosynthesis yields.We show our results for the iron peak element Mn. For this element, we compute the evolution in the three systems the Galactic bulge, the Solar neighbourhood Sagittarius; we find that to reproduce simultaneously the measurements of [Mn/Fe] versus [Fe/H] in the three systems the type Ia supernova Mn yield mus be metallicity‐dependent.We adopt two chemical evolution models for the the evolution of C and O abundances in the bulge in the thin disk. They assume the same nucleosynthesis prescriptions but different histories of star formation. In our models we consider yields from massive stars with without the inclusion of metallicity‐dependent stellar winds. The observed increase in the [C/O] with metallicity in the bulge lies between the predictions utilizing mass‐loss rates of Maeder Meynet & Maeder. A model without metallicity‐dependent yields completely fails to match the observations. Thus, the relative increase in carbon abundance at high metallicity appears to come from metallicity‐dependent stellar winds in massive stars.In the case of the neutron capture elements the comparison between the results of our standard chemical evolution model for the Milky Way halo the neutron capture abundances shown in the halo stars, indicates how to constrain the r‐process contribution by massive stars to the enrichment of these elements, keeping fixed a s‐process contribution by low mass stars, based on the theoretical results of the group of prof. Gallino. We show the results we obtain using these prescriptions for barium in the Bulge of our Galaxy, compared to the very recent measurements of this neutron capture elements by Bensby et al. based on microlensing effect in bulge stars.