Abstract
We present a chemical evolution model for the Galaxy which assumes that the evolution of the halo and thick disk is completely disentangled from the thin disk. The Galaxy formed by two main infall episodes which formed the halo-thick disk and thin disk, respectively. The model predicts the evolution of the gas mass, the star formation rate, the supernova rates and the abundances of 16 chemical elements as functions of time and galactocentric distance. Our results , strongly suggest that the previous picture for the Galaxy formation in which the gas shed from the halo was the main contributor to the thin disk formation, is not valid. We conclude a timescale of 8 Gyr for the thin-disk formation in the solar vicinity is required, implying that the infalling gas forming the thin-disk comes not only from the thick disk but mainly from the intergalactic medium. We constrain the IMF variation, Deuterium primordial value and earliest phases of Galaxy evolution.
