The Extreme Ends of the Metallicity Distribution in dSph Galaxies

Abstract

This paper reviews recent abundance results of local dSph giants. All dSph systems seem to show evidence of slow star formation rates, compared to the Milky Way, based on the most metal-rich stars exhibiting low [even-Z/Fe] ratios and high [s-process/r-process] ratios. The most metal-poor stars in the Draco, Ursa Minor, Sextans and Sculptor dSphs seem to show a split in their light even-Z, Mg and O, and the heavier even-Z, Ca and Ti, abundance ratios, where the light even-Z are halo like and the heavier even-Z elements exhibit sub-halo abundance ratios. This split remains a mystery. A review of the first dSph abundance results from FLAMES+GIRAFFE on the VLT and HRS on the Hobby-Eberly Telescope shows that the study of chemical evolution of dSph galaxies is rapidly moving out of infancy and into an era requiring very large surveys and/or targeted studies.