Determining the full satellite population of a Milky Way-mass halo in a highly resolved cosmological hydrodynamic simulation

Abstract

We investigate the formation of the satellite galaxy population of a Milky Way-mass halo in a very highly resolved magneto-hydrodynamic cosmological zoom-in simulation (baryonic mass resolution mb = 800 $\rm M_{\odot }$). We show that the properties of the central star-forming galaxy, such as the radial stellar surface density profile and star formation history, are: i) robust to stochastic variations associated with the so-called ‘Butterfly Effect’; and ii) well converged over 3.5 orders of magnitude in mass resolution. We find that there are approximately five times as many satellite galaxies at this high resolution compared to a standard ($m_b\sim 10^{4-5}\, \rm M_{\odot }$) resolution simulation of the same system. This is primarily because 2/3rds of the high resolution satellites do not form at standard resolution. A smaller fraction (1/6th) of the satellites present at high resolution form and disrupt at standard resolution; these objects are preferentially low-mass satellites on intermediate- to low-eccentricity orbits with impact parameters ≲ 30 kpc. As a result, the radial distribution of satellites becomes substantially more centrally concentrated at higher resolution, in better agreement with recent observations of satellites around Milky Way-mass haloes. Finally, we show that our galaxy formation model successfully forms ultra-faint galaxies and reproduces the stellar velocity dispersion, half-light radii, and V-band luminosities of observed Milky Way and Local Group dwarf galaxies across 6 orders of magnitude in luminosity (103-$10^{9}\, \rm L_{\odot }$).

Exploring the effect of baryons on the radial distribution of satellite galaxies with GAMA and IllustrisTNG

“…The agreement between the distributions of well-resolved satellites at differing resolution matches the conclusions of Grand et al (2021) with the simulations. However, as shown in that work, this consistency is likely to break down for satellites with very few stellar particles.…”

Snowmass2021 Cosmic Frontier White Paper: Dark Matter Physics from Halo Measurements

“…Our understanding of the dark matter halos that host ultra-faints has significantly improved over the last decade. In particular, hydrodynamical simulations have started to resolve the formation and evolution of UFDs in a cosmological context, including as satellites of larger hosts [443][444][445][446][447][448]. In parallel, semi-analytic and empirical galaxy-halo connection models have been combined with observations to infer ultra-faints' halo properties; in these models, the number of observable ultra-faints suggests that these systems occupy halos with masses down to ∼ 10 8 M (near the "atomic cooling limit"; [436,437,449,450]) or even lower [451,452].…”

Structural Parameters and Possible Association of the Ultra-faint Dwarfs Pegasus III and Pisces II from Deep Hubble Space Telescope Photometry

“…While there is much to learn from studying any of these faint satellites, examining the relatively isolated UFDs at larger Galactocentric distances is particularly useful, as they are more comparable to those produced in most simulations that resolve down to the UFD mass level (M vir ; 10 9 M e at z = 0) (e.g., Jeon et al 2017Jeon et al , 2021aJeon et al , 2021bWheeler et al 2019). More recently, Applebaum et al (2021) and Grand et al (2021) were also able to resolve down to UFD mass scale using cosmological Milky Way (MW) zoom-in simulations. Comparing the properties of observed UFDs to both of these types of simulations could help us to disentangle the effects that host galaxies may have on their satellite UFDs.…”