Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. II. Ages, metallicities, detailed elemental abundances, and connections to the Galactic thick disc

Abstract

The Bulge is the least understood major stellar population of the Milky Way. Most of what we know about the formation and evolution of the Bulge comes from bright giant stars. [ABRIDGED] We perform a detailed elemental abundance analysis based on equivalent width measurements from high-resolution spectra that were obtained while Bulge dwarf stars were optically magnified during microlensing events. [ABRIDGED] We present detailed elemental abundances and stellar ages for six new dwarf stars in the Galactic bulge. Combining these with previous events, which we have re-analysed using the same methods, we study a homogeneous sample of 15 microlensed dwarf and subgiant stars in the Bulge, which constitute the largest sample to date of microlensed dwarf stars in the Galactic bulge. The stars span the full range of metallicities from [Fe/H]=-0.72 to _s160.54, and their average metallicity is =-0.08pm 0.47, close to the average metallicity based on giant stars in the Bulge. Furthermore, the stars follow well-defined abundance trends, that for [Fe/H]