Signatures of radial migration in barred galaxies: Azimuthal variations in the metallicity distribution of old stars

TL;DR

This study uses N-body simulations to demonstrate that radial migration caused by bars and spiral arms creates observable azimuthal metallicity variations in galaxy disks, serving as indicators of ongoing migration.

Contribution

It reveals that azimuthal metallicity inhomogeneities are signatures of active radial migration in barred galaxies, a novel diagnostic for galaxy evolution studies.

Findings

Azimuthal metallicity variations are linked to strong radial migration.

These variations diminish as the bar weakens and migration subsides.

Metallicity inhomogeneities can be detected in the Milky Way and external galaxies.

Abstract

By means of N-body simulations, we show that radial migration in galaxy disks, induced by bar and spiral arms, leads to significant azimuthal variations in the metallicity distribution of old stars at a given distance from the galaxy center. Metals do not show an axisymmetric distribution during phases of strong migration. Azimuthal variations are visible during the whole phase of strong bar phase, and tend to disappear as the effect of radial migration diminishes, together with a reduction in the bar strength. These results suggest that the presence of inhomogeneities in the metallicity distribution of old stars in a galaxy disk can be a probe of ongoing strong migration. Such signatures may be detected in the Milky Way by Gaia (and complementary spectroscopic data), as well as in external galaxies, by IFU surveys like CALIFA and ATLAS3D. Mixing - defined as the tendency toward a homogeneous, azimuthally symmetric, stellar distribution in the disk - and migration turns out to be two distinct processes, the effects of mixing starting to be visible when strong migration is over.