  Dwarf Galaxies are the most common objects in the Universe and are believed
to contain large amounts of dark matter. There are mainly three morphologic
types of dwarf galaxies: dwarf ellipticals, dwarf spheroidals and dwarf
irregulars. Dwarf irregular galaxies are particularly interesting in dwarf
galaxy evolution, since dwarf spheroidal predecessors could have been very
similar to them. Therefore, a mechanism linked to gas-loss in dwarf irregulars
should be observed, i.e. ram pressure stripping. In this paper, we study the
interaction between the ISM of a dwarf galaxy, and a flowing IGM. We derive the
weak-shock, plasmon solution corresponding to the balance between the post-bow
shock pressure and the pressure of the stratified ISM (which we assume follows
the fixed stratification of a gravitationally dominant dark matter halo). We
compare our model with previously published numerical simulations and with the
observed shape of the HI cloud around the Ho II and Pegasus dwarf irregular
galaxies. We show that such a comparison provides a straightforward way for
estimating the Mach number of the impinging flow.
