Milky Way Metallicities and Fossil Cosmology

Abstract

Taking into account the structural characteristics of the Milky Way stellar populations leads us to reconsider our concepts of the chemical evolution of our Galaxy. In particular it is suggested that the solar vicinity provides an unrepresentative sampling of the disk MDF and that no G-dwarf problem generalizable to the whole disk can be inferred from the solar vicinity, nor constrains on the infall time scale. I suggest that the best place to look for an unbiased and representative disk MDF is the Galactic bulge, and show how the chemical properties of the disk and the bulge can be reconciled. A new way to measure the SFH of the Galaxy shows that the thick disk is massive, supporting the mass deduced from structural properties. A massive thick disk population implies that large amounts of gas were present at early times, in contradiction with the long infall time scales inferred by standard chemical evolution models. Finally, comparisons of the MW with the mass growth history of similar galaxies at high redshift suggest that the thick disk is not a contingent population, but may be generic to all galaxies of the class of the Milky Way.