Are dwarf spheroidal galaxies dark matter dominated or remnants of disrupted larger satellite galaxies? A possible test

The failure of standard cosmological models in accounting for the statistics of dwarf satellites and the rotation curve of gas-rich dwarf galaxies in detail has led us to examine whether earlier nonequilibrium models of dwarf spheroidal satellites without any dark matter should be reconsidered in more detail. Such models can explain the high dispersion of the dwarf spheroids by the projection of disrupted tidal debris. We show in the case of Milky Way satellites that these models predict a significant spread in the apparent magnitude of horizontal-branch (HB) stars that is correlated with sky position and velocity. In particular, the models produce a strong correlation of radial velocity with the long axis of the dwarf. Current data do not set strong enough constraints on models, but we suggest that photometric and spectroscopic surveys of extratidal stars of nearby dwarf spheroids in the Milky Way and Andromeda galaxies can falsify these models without dark matter.