Chemical enrichment and radial migration in the Galactic disc – the origin of the [αFe] double sequence

The $([\alpha/{\rm Fe}],[{\rm Fe/H}])$ distribution of Milky Way stars shows at least two distinct sequences, which have traditionally been associated with the thin and thick disc components. abundance varies systematically location $R$ $|z|$ across Galaxy. Using an analytical chemodynamical model that includes effects radial migration kinematic heating, we show it is possible to reproduce observed different locations. Unlike some earlier models, our scheme does not require a component emerging from separate evolutionary path. proposed has continuous star formation history age velocity dispersion relation. Moreover, [$\alpha$/Fe] constant for stellar ages less than 8 Gyr, but increases sharply older over time scale 1.5 Gyr. gap between sequences due this sharp transition. We high-[$\alpha$/Fe] sequence low metallicity end simply pile-up old stars. At high end, find having similar birth radius originated in inner disc. Our successfully explains uniformity locus low-[$\alpha$/Fe] contains radii owes its existence migration. For sequence, angular momentum anti-correlated [Fe/H], can trend Galactic If included, fails generate double instead only single sequence. simple major advantages as show.