Quenching of satellite galaxies of Milky Way analogues: reconciling
  theory and observations
  The vast majority of low-mass satellite galaxies around the Milky Way and M31
appear virtually devoid of cool gas and show no signs of recent or ongoing star
formation. Cosmological simulations demonstrate that such quenching is expected
and is due to the harsh environmental conditions that satellites face when
joining the Local Group (LG). However, recent observations of Milky Way
analogues in the SAGA survey present a very different picture, showing the
majority of observed satellites to be actively forming stars, calling into
question the realism of current simulations and the typicality of the LG. Here
we use the ARTEMIS suite of high-resolution cosmological hydrodynamical
simulations to carry out a careful comparison with observations of dwarf
satellites in the LG, SAGA, and the Local Volume (LV) survey. We show that
differences between SAGA and the LG and LV surveys, as well as between SAGA and
the ARTEMIS simulations, can be strongly reduced by considering differences in
the host mass distributions and (more importantly) observational selection
effects, specifically that low-mass satellites which have only recently been
accreted are more likely to be star-forming, have a higher optical surface
brightness, and are therefore more likely to be included in the SAGA survey.
This picture is confirmed using data from the deeper LV survey, which shows
pronounced quenching at low masses, in accordance with the predictions of
LCDM-based simulations.
