Luminosity Functions and Host-to-Host Scatter of Dwarf Satellite Systems
  in the Local Volume
  Low-mass satellites around Milky Way (MW)-like galaxies are important probes
of small scale structure and galaxy formation. However, confirmation of
satellite candidates with distance measurements remains a key barrier to fast
progress in the Local Volume (LV). We measure the surface brightness
fluctuation (SBF) distances to recently cataloged candidate dwarf satellites
around 10 massive hosts within $D<12$ Mpc to confirm association. The satellite
systems of these hosts are complete and mostly cleaned of contaminants down to
$M_g{\sim}-9$ to $-10$, within the area of the search footprints. Joining this
sample with hosts surveyed to comparable or better completeness in the
literature, we explore how well cosmological simulations combined with common
stellar to halo mass relations (SHMR) match observed satellite luminosity
functions in the classical satellite luminosity regime. Adopting a SHMR that
matches hydrodynamic simulations, the predicted overall satellite abundance
agrees well with the observations. The MW is remarkably typical in its
luminosity function amongst LV hosts. Contrary to recent results, we find that
the host-to-host scatter predicted by the model is in close agreement with the
scatter between the observed systems, once the different masses of the observed
systems are taken into account. However, we find significant evidence that the
observed systems have more bright and fewer faint satellites than the SHMR
model predicts, necessitating a higher normalization of the SHMR around halo
masses of $10^{11}$ \msun\ than present in common SHMRs. These results
demonstrate the utility of nearby satellite systems in inferring the
galaxy-subhalo connection in the low-mass regime.
