  Milky Way dwarf spheroidal galaxies are the tiniest observed galaxies and are
currently associated with the largest fractions of dark matter, which is
revealed by their too large velocity dispersions. However, most of them are
found near their orbital pericenters. This leads to a very low probability, P =
2 $10^{-7}$, that they could be long-lived satellites such as sub-halos
predicted by cosmological simulations. Their proximity to their pericenters
suggests instead that they are affected by tidal shocks, which provide
sufficient kinematic energy to explain their high velocity dispersions.
Dependency of the dark matter properties to their distance to the Milky Way
appears to favor tidally shocked and out of equilibrium dSphs instead of
self-equilibrium systems dominated by dark matter.
