I. Minchev, C. Chiappini, M. Martig
(Abridged) We present a new approach for studying the chemodynamical evolution in disc galaxies, which consists of fusing disc chemical evolution models with compatible numerical simulations of galactic discs. Such a method avoids known star formation and chemical enrichment problems encountered in simulations. Here we focus on the Milky Way, by using a detailed thin-disc chemical evolution model (matching local observables, weakly affected by radial migration) and a simulation in the cosmological context, with dynamical properties close to those of our Galaxy. We examine in detail the interplay between in-situ chemical enrichment and radial migration, and their impact on key observables in the solar neighborhood, e.g., the age-metallicity-velocity relation, the metallicity distribution, and gradients in the radial and vertical directions. We show that, due to radial migration from mergers at high redshift and the central bar at later times, a sizable fraction of old metal-poor, high-[alpha/Fe] stars can reach the solar vicinity. This naturally accounts for a number of observations related to both the thin and thick discs, despite the fact that we use thin-disc chemistry only. Although significant radial mixing is present, a slope in the AVR is preserved, with a scatter compatible with recent observational work. While we find a smooth density distribution in the [O/Fe]-[Fe/H]-plane, we can recover the observed discontinuity by selecting particles according to kinematical criteria used in high-resolution samples to define the thin and thick discs. We show that in the absence of early-on massive mergers the vertical velocity dispersion of the oldest stars is underestimated by a factor of ~2 compared to observations. Finally, we offer a new, unifying model for the Milky Way thick disc, where both mergers and radial migration play a role at different stages of the disc evolution.
View original:
http://arxiv.org/abs/1208.1506
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