The Evolution of Heavy Elements in Dwarf Spheroidal Galaxies

Abstract

We follow the evolution of barium and europium in four Local Group Dwarf Spheroidal Galaxies by means of a detailed chemical evolution model. The model adopts up to date nucleosynthesis and takes into account the role played by supernovae of different types (II, Ia). By assuming that barium is produced in low mass AGB stars by s-process but also in massive stars (in the mass range 10–30 M_{[odot ]}) by r-process and that europium is a pure r-process element synthesized in massive stars in the same range of masses (10–30 M_{[odot ]}), we are able to reproduce the observed [Ba/Fe] and [Eu/Fe] as functions of [Fe/H] in all four galaxies studied. We confirm also the important role played by the very low star formation efficiencies (ν = 0.005–0.5 Gyr⁻¹) and by the intense galactic winds (w_i = 6–13) in the evolution of these galaxies.