Globular clusters as tracers of the dark matter content of dwarfs in
  galaxy clusters
  Globular clusters (GCs) are often used to estimate the dark matter content of
galaxies, especially dwarfs, where other kinematic tracers are lacking. These
estimates typically assume spherical symmetry and dynamical equilibrium,
assumptions that may not hold for the sparse GC population of dwarfs in galaxy
clusters. We use a catalog of GCs tagged onto the Illustris simulation to study
the accuracy of GC-based mass estimates. We focus on galaxies in the stellar
mass range 10$^{8} - 10^{11.8}$ M$_{\odot}$ identified in $9$ simulated
Virgo-like clusters. Our results indicate that mass estimates are, on average,
quite accurate in systems with GC numbers $N_{\rm GC} \geq 10$ and where the
uncertainty of individual GC line-of-sight velocities is smaller than the
inferred velocity dispersion, $\sigma_{\rm GC}$. In cases where $N_{\rm GC}
\leq 10$, however, biases may result depending on how $\sigma_{\rm GC}$ is
computed. We provide calibrations that may help alleviate these biases in
methods widely used in the literature. As an application, we find a number of
dwarfs with $M_{*} \sim 10^{8.5}\, M_{\odot}$ (comparable to the ultradiffuse
galaxy DF2, notable for the low $\sigma_{GC}$ of its $10$ GCs) with
$\sigma_{\rm GC} \sim 7$ - $15\; \rm km \rm s^{-1}$. These DF2 analogs
correspond to relatively massive systems at their infall time ($M_{200} \sim 1$
- $3 \times 10^{11}$ $M_{\odot}$) which have retained only $3$-$17$ GCs and
have been stripped of more than 95$\%$ of their dark matter. Our results
suggest that extreme tidal mass loss in otherwise normal dwarf galaxies may be
a possible formation channel for ultradiffuse objects like DF2.
