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ABSTRACT We investigate the formation of the satellite galaxy population of a Milky Way-mass halo in a very highly resolved magnetohydrodynamic cosmological zoom-in simulation (baryonic mass resolution mb = 800 M). 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 (mb 10^4-5\, M) resolution simulation of the same system. This is primarily because two-thirds of the high-resolution satellites do not form at standard resolution. A smaller fraction (one-sixth) 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 six orders of magnitude in luminosity (103–10^9\, L).
Grand et al. (Fri,) studied this question.