Riding the Spiral Waves: Implications of Stellar Migration for the Properties of Galactic Disks

TL;DR

This paper uses high-resolution simulations to show that stars in spiral galaxy disks can migrate significantly from their birthplaces, affecting interpretations of stellar populations and galaxy evolution models.

Contribution

It demonstrates that stellar radial migration occurs via resonant scattering with spiral arms, challenging the assumption that stars stay near their birth radii.

Findings

Radial migration explains flat age-metallicity relations.

Migration accounts for the scarcity of metal-poor stars locally.

Impacts the interpretation of extragalactic stellar populations.

Abstract

Stars in disks of spiral galaxies are usually assumed to remain roughly at their birth radii. This assumption is built into decades of modelling of the evolution of stellar populations in our own Galaxy and in external systems. We present results from self-consistent high-resolution $N$-body + Smooth Particle Hydrodynamics simulations of disk formation, in which stars migrate across significant galactocentric distances due to resonant scattering with transient spiral arms, while preserving their circular orbits. We investigate the implications of such migrations for observed stellar populations. Radial migration provides an explanation for the observed flatness and spread in the age-metallicity relation and the relative lack of metal poor stars in the solar neighborhood. The presence of radial migration also prompts rethinking of interpretations of extra-galactic stellar population data, especially for determinations of star formation histories.