Star formation histories of dwarf galaxies in the FIRE simulations:
  dependence on mass and Local Group environment
  We study star formation histories (SFHs) of $\simeq500$ dwarf galaxies
(stellar mass $M_\ast = 10^5 - 10^9\,M_\odot$) from FIRE-2 cosmological zoom-in
simulations. We compare dwarfs around individual Milky Way (MW)-mass galaxies,
dwarfs in Local Group (LG)-like environments, and true field (i.e. isolated)
dwarf galaxies. We reproduce observed trends wherein higher-mass dwarfs quench
later (if at all), regardless of environment. We also identify differences
between the environments, both in terms of "satellite vs. central" and "LG vs.
individual MWvs. isolated dwarf central." Around the individual MW-mass hosts,
we recover the result expected from environmental quenching: central galaxies
in the "near field" have more extended SFHs than their satellite counterparts,
with the former more closely resemble isolated ("true field") dwarfs (though
near-field centrals are still somewhat earlier forming). However, this
difference is muted in the LG-like environments, where both near-field centrals
and satellites have similar SFHs, which resemble satellites of single MW-mass
hosts. This distinction is strongest for $M_\ast = 10^6 - 10^7\,M_\odot$ but
exists at other masses. Our results suggest that the paired halo nature of the
LG may regulate star formation in dwarf galaxies even beyond the virial radii
of the MW and Andromeda. Caution is needed when comparing zoom-in simulations
targeting isolated dwarf galaxies against observed dwarf galaxies in the LG.
