Impacts of Radial Mixing on the Galactic Thick and Thin Disks

摘要

Using N-body simulations of the Galactic disks, we qualitatively study howthe metallicity distributions of the thick and thin disk stars are modified byradial mixing induced by the bar and spiral arms. We show that radial mixingdrives a positive vertical metallicity gradient in the mono-age disk populationwhose initial scale-height is constant and initial radial metallicity gradientis tight and negative. On the other hand, if the initial disk is flaring, withscale-height increasing with galactocentric radius, radial mixing leads to anegative vertical metallicity gradient, which is consistent with the currentobserved trend. We also discuss impacts of radial mixing on the metallicitydistribution of the thick disk stars. By matching the metallicity distributionof N-body models to the SDSS/APOGEE data, we argue that the progenitor of theMilky Way's thick disk should not have a steep negative metallicity gradient.