Does dark matter protect cluster dwarf galaxies from disruption?

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High ratios of dark to luminous mass appear to be typical for dwarf spheroidal galaxies, not only as Milky Way satellites: Recently it was shown that these faint, diffuse galaxies would be disrupted in the Perseus cluster center if they did not contain a major amount of dark matter. However, in both environments the argumentation hinges on a critical assumption: the galaxies need to be in an equilibrium state. If they are instead in the process of disruption, no significant dark matter content could be inferred, making the dwarfs a crucial test for our understanding of galaxy formation in the cosmological context. Deep imaging will reveal tidal tails and signs of disruption around these galaxies – or provide a strong confirmation on the presence of unseen mass and therefore of CDM in general.