Stellar migration in the Auriga simulations

Okalidis, Periklis; Grand, Robert J. J.; Yates, Robert M.; Springel, Volker
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Monthly Notices of the Royal Astronomical Society

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We study the presence and importance of stellar migration in the evolution of 17 Milky-Way like disc galaxies with stellar mass 10 < log(M*/M⊙) < 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 discs. We find several cases of age gradient flattening due to migration, but significant changes to metallicity profiles only for older stellar populations and discs that develop a strong bar. Furthermore, we study stellar migration from the perspective of the change of the galactocentric radius (ΔR) and orbital guiding centre radius (ΔRg) of stellar particles between given time intervals. We find that stars migrate approximately as a diffusion process only in the outer parts of the discs 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 parametrizations 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.
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