Radial mixing in the outer Milky Way disk caused by an orbiting satellite

TL;DR

This study uses simulations to show how satellite galaxy interactions can heat, warp, and induce radial mixing in the Milky Way's outer disk, affecting stellar orbits and metallicity distribution.

Contribution

It demonstrates that satellite perturbations can cause significant radial mixing and structural changes in the outer Galactic disk, a novel insight into galaxy evolution.

Findings

Satellite of a few billion solar masses heats the outer disk.

Perturbations excite spiral structure and warp.

Radial mixing can alter stellar metallicity distribution.

Abstract

Using test particle simulations we examine the structure of the outer Galactic disk as it is perturbed by a satellite in a tight eccentric orbit about the Galaxy. A satellite of mass a few times 10^9 Msol can heat the outer Galactic disk, excite spiral structure and a warp and induce streams in the velocity distribution. We examine particle eccentricity versus the change in mean radius between initial and current orbits. Correlations between these quantities are reduced after a few satellite pericenter passages. Stars born in the outer galaxy can be moved in radius from their birth positions and be placed in low eccentricity orbits inside their birth radii. We propose that mergers and perturbations from satellite galaxies and subhalos can induce radial mixing in the stellar metallicity distribution.