Globular clusters indicate ultra diffuse galaxies are dwarfs
  We present an analysis of archival {\it HST/ACS} imaging in the F475W
($g_{475}$), F606W ($V_{606}$) and F814W ($I_{814}$) bands of the globular
cluster (GC) system of a large (3.4 kpc effective radius) ultra-diffuse galaxy
(DF17) believed located in the Coma Cluster of galaxies. We detect 11 GCs down
to the 5$\sigma$ completeness limit of the imaging ($I_{814}=$27 mag).
Correcting for background and our detection limits yields a total population of
GCs in this galaxy of $27\pm5$ and a $V$-band specific frequency, $S_N=28\pm5$.
Based on comparisons to the GC systems of Local galaxies, we show that both the
absolute number and the colors of the GC system of DF17 are consistent with the
GC system of a dark-matter dominated dwarf galaxy with virial mass
$\sim0.9\times10^{10}$~\msun and a dark-to-stellar mass ratio, $M_{vir} / M_{
star}\sim 1000$. Based on the stellar mass-growth of the Milky Way, we show
that DF17 cannot be understood as a failed Milky Way-like system, but is more
similar to quenched Large Magellanic Cloud-like systems. We find that the mean
color of GC population, $g_{475}-I_{814}$ = $0.91\pm0.05$ mag, coincides with
the peak of the color distribution of intracluster GCs and are also similar to
those of the blue GCs in the outer regions of massive galaxies. We suggest that
both the intracluster GC population in Coma and the blue-peak in the GC
populations of massive galaxies may be fed - at least in part - by the
disrupted equivalents of systems such as DF17.
