Tidal evolution of disky dwarf galaxies: prograde versus retrograde
  orbits
  The formation of dwarf spheroidal galaxies in the Local Group from disky
progenitors via tidal interaction with a bigger host is one of the most
promising scenarios of their origin. Using N-body simulations we study the
process by following the evolution of a disky dwarf orbiting a Milky Way-like
host. We focus on the effect of the orientation of the dwarf galaxy disk's
angular momentum with respect to the orbital one. We find a strong dependence
of the efficiency of the transformation from a disk to a spheroid on the disk
orientation. The effect is strongest for the exactly prograde and weakest for
the exactly retrograde orbit. In the prograde case the stellar component forms
a strong bar and remains prolate until the end of the evolution, while its
rotation is very quickly replaced by random motions of the stars. In the
retrograde case the dwarf remains oblate, does not form a bar and loses
rotation very slowly. Our results suggest that resonant effects are the most
important mechanism underlying the evolution while tidal shocking plays only a
minor role.
