Stellar migration in the Auriga simulations

TL;DR

This study analyzes stellar migration in Milky-Way like galaxies using Auriga simulations, revealing how migration affects age and metallicity profiles and varies with galaxy features like bars, providing models for galaxy evolution simulations.

Contribution

It offers new insights into the patterns and effects of stellar migration in galaxy disks, including parametrizations for modeling migration in galaxy evolution studies.

Findings

Migration causes age gradient flattening in disks.

Metallicity profiles are significantly altered only in older stars and barred galaxies.

Migration behaves as a diffusion process mainly in outer disk regions.

Abstract

We study the presence and importance of stellar migration in the evolution of 17 Milky-Way like disk galaxies with stellar mass $10 < \textrm{log}(M_{*}/{\rm M}_\odot) < 11$ from the Auriga suite of zoom-in cosmological hydrodynamical simulations. We compare the birth radii of the stars to their radii at $z=0$ for each system and present mean values of the strength of stellar migration as a function of radius and stellar age which vary between 1-4 kpc. We also investigate the effect of migration on age and metallicity radial profiles in the disks. We find several cases of age gradient flattening due to migration, but significant changes to metallicity profiles only for older stellar populations and disks that develop a strong bar. Furthermore, we study stellar migration from the perspective of the change of the galactocentric radius ($\Delta R$) and orbital guiding centre radius ($\Delta R_g$) of stellar particles between given time intervals. We find that stars migrate approximately as a diffusion process only in the outer parts of the disks and for particular galaxies that have a weak bar. Strongly barred galaxies in our sample show larger stellar migration but its timestep evolution is slower-than-diffusion. Finally, we give parametrisations that encapsulate the dependence of the strength of the radial migration as a function of time and radius, for incorporation into (semi-)analytic models of galaxy evolution.