  Using deep HST/ACS observations of the core of the Perseus Cluster, we
identify a large population of dwarf elliptical galaxies down to M_V = -12. All
these dwarfs are remarkably smooth in appearance, showing no evidence for
internal features that could be the result of tidal processes or star formation
induced by the cluster potential. Based on these observations and the
relatively large sizes of these dwarfs, we argue that at least some must have a
large dark matter component to prevent their disruption by the cluster
potential. We further derive a new method to quantify the dark matter content
of cluster dSphs without the use of kinematics, which are impossible to obtain
at these distances. We find that mass-to-light ratios for dwarfs in the core of
the Perseus Cluster are comparable to those found for Local Group dSphs,
ranging between M/L ~ 1 and 120. This is evidence that dwarf spheroidals reside
in dark matter subhalos that protect them from tidal processes in the cores of
dense clusters.
