Dark satellites and the morphology of dwarf galaxies
  One of the strongest predictions of the LambdaCDM cosmological model is the
presence of dark satellites orbiting all types of galaxies. We focus here on
the dynamical effects of such satellites on disky dwarf galaxies, and
demonstrate that these encounters can be dramatic. Although mergers with M_sat
> M_d are not very common, because of the lower baryonic content they occur
much more frequently on the dwarf scale than for L_*-galaxies. As an example,
we present a numerical simulation of a 20% (virial) mass ratio merger between a
dark satellite and a disky dwarf (akin to the Fornax dwarf galaxy in
luminosity) that shows that the merger remnant has a spheroidal morphology. We
conclude that perturbations by dark satellites provide a plausible path for the
formation of dSph systems and also could trigger starbursts in gas rich dwarf
galaxies. Therefore the transition from disky to the often amorphous,
irregular, or spheroidal morphologies of dwarfs could be a natural consequence
of the dynamical heating of hitherto unobservable dark satellites.
