Date: 22.11.2022

Oliver Newton (CFT PAN)

Exploring the Local Group with constrained simulations

Abstract:
Exquisite observations of the galaxies in the Local Group – comprising the Milky Way, M31, and a population with lower masses – have enhanced our understanding of a variety of astrophysical processes. In this highly non-linear regime, numerical simulations have proved essential to model how these mechanisms affect the evolution of low-mass galaxies in the unique and dynamic environment of the Local Group. This is best studied in 'constrained' simulations, which embed Local Group analogues in larger-scale structure that closely corresponds to observational proxies. Using the new HESTIA suite of such simulations, I explore the properties of low-mass haloes that can be found `in the field' of the Local Group at z=0. The simulations predict the existence of a novel class of field haloes that passed through the Milky Way and M31 at early times. The unique trajectories of these 'Hermeian' haloes facilitate the exchange of material between the Milky Way and M31, and the Hermeian galaxies themselves show promise as targets for indirect dark matter searches beyond the Milky Way virial radius. I also discuss the populations of ultra-diffuse galaxies (UDGs) that form in HESTIA. These highly elusive objects could provide useful insights into the nature of dark matter and improve our understanding of the extremes of galaxy evolution. I show that UDGs could account for as much as half of the total population of field galaxies within 2.5 Mpc of the Local Group, and several could be awaiting discovery in Sloan Digital Sky Survey data that have already been collected.