Comments on the final evolutionary phase of very small dwarf spheroidal galaxies

It is known that slow baryon outflow influences the evolution of dwarf spheroidals (dSphs) around the Milky Way. However, one may ask: what dSphs are too small? Actually, the depth of the gravitational potential of very small dSphs discovered recently is estimated as the energy of only one supernova explosion. This means that the loss of interstellar medium should be fast. Then, adopting a dSph formation scenario, which considers the fast baryon loss, we investigate which mass loss is important. According to our estimates, when only baryon mass loss is considered, the observational radius is larger than that expected in that scenario for all of the very small dSphs. This indicates that the expansion of the system is caused by slow dark matter outflow.