Ultra-faint dwarfs in a Milky Way context: Introducing the Mint
  Condition DC Justice League Simulations
  We present results from the "Mint" resolution DC Justice League suite of
Milky Way-like zoom-in cosmological simulations, which extend our study of
nearby galaxies down into the ultra-faint dwarf (UFD) regime for the first
time. The mass resolution of these simulations is the highest ever published
for cosmological Milky Way zoom-in simulations run to $z=0$, with initial star
(dark matter) particle masses of 994 (17900) M$_\odot$, and a force resolution
of 87 pc. We study the surrounding dwarfs and UFDs, and find the simulations
match the observed dynamical properties of galaxies with $-3 < M_V < -19$, and
reproduce the scatter seen in the size-luminosity plane for $r_h\gtrsim200$ pc.
We predict the vast majority of nearby galaxies will be observable by the Vera
Rubin Observatory's co-added Legacy Survey of Space and Time (LSST). We
additionally show that faint dwarfs with velocity dispersions $\lesssim5$ km/s
result from severe tidal stripping of the host halo. We investigate the
quenching of UFDs in a hydrodynamical Milky Way context, and find that the
majority of UFDs are quenched prior to interactions with the Milky Way, though
some of the quenched UFDs retain their gas until infall. Additionally these
simulations yield some unique dwarfs that are the first of their kind to be
simulated, e.g., an HI-rich field UFD, a late-forming UFD that has structural
properties similar to Crater 2, as well as a compact dwarf satellite that has
no dark matter at $z=0$.
