Can cosmological simulations capture the diverse satellite populations of observed Milky Way analogues?

Abstract

ABSTRACT The recent advent of deep observational surveys of local Milky Way ‘analogues’ and their satellite populations allows us to place the Milky Way in a broader cosmological context and to test models of galaxy formation on small scales. In this study, we use the Lambda cold dark matter (ΛCDM)-based ARTEMIS suite of cosmological hydrodynamical simulations containing 45 Milky Way analogue host haloes to make comparisons to the observed satellite luminosity functions, radial distribution functions, and abundance scaling relations from the recent Local Volume and SAGA observational surveys, in addition to the Milky Way and M31. We find that, contrary to some previous claims, ΛCDM-based simulations can successfully and simultaneously capture the mean trends and the diversity in both the observed luminosity and radial distribution functions of Milky Way analogues once important observational selection criteria are factored in. Furthermore, we show that, at fixed halo mass, the concentration of the simulated satellite radial distribution is partly set by that of the underlying smooth dark matter halo, although stochasticity due to the finite number of satellites is the dominant driver of scatter in the radial distribution of satellites at fixed halo mass.