  We study satellite counts and quenched fractions for satellites of Milky Way
analogs in Romulus25, a large-volume cosmological hydrodynamic simulation.
Depending on the definition of a Milky Way analog, we have between 66 and 97
Milky Way analogs in Romulus25, a 25 Mpc per-side uniform volume simulation. We
use these analogs to quantify the effect of environment and host properties on
satellite populations. We find that the number of satellites hosted by a Milky
Way analog increases predominantly with host stellar mass, while environment,
as measured by the distance to a Milky Way-mass or larger halo, may have a
notable impact in high isolation. Similarly, we find that the satellite
quenched fraction for our analogs also increases with host stellar mass, and
potentially in higher-density environments. These results are robust for
analogs within 3 Mpc of another Milky Way-mass or larger halo, the
environmental parameter space where the bulk of our sample resides. We place
these results in the context of observations through comparisons to the
Exploration of Local VolumE Satellites and Satellites Around Galactic Analogs
surveys. Our results are robust to changes in Milky Way analog selection
criteria, including those that mimic observations. Finally, as our samples
naturally include Milky Way-Andromeda pairs, we examine quenched fractions in
pairs vs isolated systems. We find potential evidence, though not conclusive,
that pairs, defined as being within 1 Mpc of another Milky Way-mass or larger
halo, may have higher satellite quenched fractions.
