The chemodynamical evolution of the Milky Way disc - A new modeling approach

Despite the recent advancements in the field of galaxy formation and evolution, fully self-consistent simulations are still unable to make the detailed predictions necessary for the planned and ongoing large spectroscopic and photometric surveys of the Milky Way disc. These difficulties arise from the very uncertain nature of sub-grid physical energy feedback within models, affecting both star formation rates and chemical enrichment. To avoid these problems, we have introduced a new approach which consists of fusing disc chemical evolution models with compatible numerical simulations. We demonstrate the power of this method by showing that a range of observational results can be explained by our new model. 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 recent observations related to both the thin and thick discs, despite the fact that we use thin-disc chemistry only. Within the framework of our model, the MW thick disc has emerged naturally from (i) stars born with high velocity dispersions at high redshift, (ii) stars migrating from the inner disc very early on due to strong merger activity, and (iii) further radial migration driven by the bar and spirals at later times. A significant fraction of old stars with thick-disc characteristics could have been born near the solar radius.