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

Grand, Robert J.J. and Marinacci, Federico and Pakmor, Rüdiger and Simpson, Christine M. and Kelly, Ashley J. and Gómez, Facundo A. and Jenkins, Adrian and Springel, Volker and Frenk, Carlos S. and White, Simon D.M. (2021) 'Determining the full satellite population of a Milky Way-mass halo in a highly resolved cosmological hydrodynamic simulation.', Monthly Notices of the Royal Astronomical Society, 507 (4). pp. 4953-4967.


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∼104−5M⊙⁠) 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 (103–109L⊙⁠).

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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2021 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:30 August 2021
Date deposited:15 November 2021
Date of first online publication:03 September 2021
Date first made open access:15 November 2021

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