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 _ { \odot } /L _ { \odot } \approx 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 .