On stellar migration from Andromeda to the Milky Way

Abstract

ABSTRACT Recent Gaia observations suggest that some hypervelocity stars (HVSs) might originate from outside the Galaxy. We ask whether these HVSs could come from as far as Andromeda. Therefore, we simulate HVSs originating in Andromeda with initial conditions based on attributes of high-velocity stars measured in the Milky Way and a simple model for the gravitational potential of Andromeda and the Milky Way. We evaluate the validity of this scenario based on the simulation results. While we expect that the vast majority of HVSs in our Galaxy will originate here, we expect the number of stars present from Andromeda at any one time to be between 12 and 3910, depending upon model assumptions. Further, we analyse the properties of HVSs that are able to reach the Milky Way. We discuss whether they could be detected experimentally based on recent constraints set on the ejection rate of HVSs from the Milky Way centre.