High-precision Mg abundances in the metal-rich Galactic disc: chemodynamical relations and comparison with chemical evolution models

Abstract

The [Mg/Fe] abundance ratios are a fundamental fossil signature in Galactic archaeology for tracing the chemical evolution of disc stellar populations. High-precision chemical abundances, accurate stellar ages, distances, and dynamical data, together with their direct comparison with theoretical models, are crucial to infer the Milky Way formation history. We derived new more precise [Mg/Fe] abundances from the AMBRE:HARPS dataset, and estimated ages and dynamical properties using Gaia DR2 data. The data are compared with detailed chemical evolution models for the Milky Way, exploring different formation scenarios for the Galactic disc (i.e. the delayed two-infall and the parallel models). Our data favour the rapid formation of an early disc that settled in the inner regions, followed by the accretion of external metal-poor gas. The bulk of the data are well reproduced by the parallel and two-infall scenarios, but both scenarios have problems in explaining the most metal-rich and metal-poor tails of the low-$\alpha$ stars, which can be explained in light of radial migration from the inner and outer disc regions, respectively.%.