18 February 2020A census of the orbital properties of the M31 satellites

Laura WATKINS
MPIA Heidelberg, Allemagne

Two members of the M31 satellite population, And XII and And XIV, have extremely high line-of-sight velocities and it has been suggested that they are on their first infall into the M31 system. To confirm this prediction, we need to study their orbits. Cosmological simulations of hierarchical structure formation predict that dark matter forms a complex network of filaments and sheets. As subhalos are accreted onto a massive host halo along these filaments, we expect to see groups of satellites orbiting with similar orbital properties. To find orbiting groups, we need to determine orbits for the satellites and look for similarities. I will present an analysis of the dynamics of the M31 satellite system. To account for the lack of proper motion measurements for the satellites, we use a combination of the timing argument and phase-space distribution functions. I will show that the bulk of the population are well described by our models with the exception of And XII and And XIV, which suggests that they are indeed recent accretions to M31. Among the rest of the population, I will describe the identification of four candidate infall groups.