An Excess of Globular Clusters in UDGs Formed Through Tidal Heating
  To investigate the origin of elevated globular cluster abundances observed
around Ultra-Diffuse Galaxies (UDGs), we simulate globular cluster populations
hosted by UDGs formed through tidal heating. Specifically, globular cluster
(GC) formation is modeled as occurring in regions of dense star formation.
Because star-formation-rate-densities are higher at high redshift, dwarf
galaxies in massive galaxy clusters, which formed most of their stars at high
redshift, form a large fraction of their stars in globular clusters. Given that
UDGs formed through environmental processes are more likely to be accreted at
high redshift, these systems have more GCs than non-UDGs. In particular, our
model predicts that massive UDGs have twice the GC mass of non-UDGs of similar
stellar mass, in rough agreement with observations. Although this effect is
somewhat diminished by GC disruption, we find that the relationship between GC
mass fraction and cluster-centric distance, and the relationship between GC
mass fraction and galaxy half-light radius are remarkably similar to
observations. Among our model objects, both UDGs and non-UDGs present a
correlation between halo mass and GC mass, although UDGs have lower dynamical
masses at a given GC mass. Furthermore, because of the effectiveness of GC
disruption, we predict that GCs around UDGs should have a more top heavy mass
function than GCs around non-UDGs. This analysis suggests that dwarfs with
older stellar populations, such as UDGs, should have higher globular cluster
mass fractions than objects with young stellar populations, such as isolated
dwarfs.
