By means of N-body simulations, we show that radial migration in galaxydisks, induced by bar and spiral arms, leads to significant azimuthalvariations in the metallicity distribution of old stars at a given distancefrom the galaxy center. Metals do not show an axisymmetric distribution duringphases of strong migration. Azimuthal variations are visible during the wholephase of strong bar phase, and tend to disappear as the effect of radialmigration diminishes, together with a reduction in the bar strength. Theseresults suggest that the presence of inhomogeneities in the metallicitydistribution of old stars in a galaxy disk can be a probe of ongoing strongmigration. Such signatures may be detected in the Milky Way by Gaia (andcomplementary spectroscopic data), as well as in external galaxies, by IFUsurveys like CALIFA and ATLAS3D. Mixing - defined as the tendency toward ahomogeneous, azimuthally symmetric, stellar distribution in the disk - andmigration turns out to be two distinct processes, the effects of mixingstarting to be visible when strong migration is over.
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