What velocities and eccentricities tell us about radial migration

Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany

^a e-mail: rasch@mpa-garching.mpg.de

Abstract

This note attempts to interpret some of the recent findings about a downtrend in the mean azimuthal velocity of low [α/Fe] thin disc stars with increasing metallicity. The presence of such a trend was predicted in the model of [19], albeit with a slightly steeper slope. We show that in a simple picture a Galactic disc without mixing in angular momenta would display an exceedingly steep trend, while in the case of complete mixing of all stars the trend has to vanish. The difference between model and observational data can hence be interpreted as the consequence of the radial abundance gradient in the model being too high resulting in an underestimate of the migration strength. We shortly discuss the value of eccentricity distributions in constraining structure and history of the Galactic disc.