Extending the Globular Cluster System-Halo Mass Relation to the Lowest
  Galaxy Masses
  High mass galaxies, with halo masses $M_{200} \ge 10^{10} M_{\odot}$, reveal
a remarkable near-linear relation between their globular cluster (GC) system
mass and their host galaxy halo mass. Extending this relation to the mass range
of dwarf galaxies has been problematic due to the difficulty in measuring
independent halo masses. Here we derive new halo masses based on stellar and HI
gas kinematics for a sample of nearby dwarf galaxies with GC systems. We find
that the GC system mass--halo mass relation for galaxies populated by GCs holds
from halo masses of $M_{200} \sim 10^{14} M_{\odot}$ down to below $M_{200}$
$\sim 10^9 M_{\odot}$, although there is a substantial increase in scatter
towards low masses. In particular, three well-studied ultra diffuse galaxies,
with dwarf-like stellar masses, reveal a wide range in their GC-to-halo mass
ratios. We compare our GC system--halo mass relation to the recent model of El
Badry et al., finding that their fiducial model does not reproduce our data in
the low mass regime. This may suggest that GC formation needs to be more
efficient than assumed in their model, or it may be due to the onset of
stochastic GC occupation in low mass halos. Finally, we briefly discuss the
stellar mass-halo mass relation for our low mass galaxies with GCs, and we
suggest some nearby dwarf galaxies for which searches for GCs may be fruitful.
