The major merger origin of the Andromeda II kinematics
  Prolate rotation (i.e. rotation around the long axis) has been reported for
two Local Group dwarf galaxies: Andromeda II, a dwarf spheroidal satellite of
M31, and Phoenix, a transition type dwarf galaxy. The prolate rotation may be
an exceptional indicator of a past major merger between dwarf galaxies. We
showed that this type of rotation cannot be obtained in the tidal stirring
scenario, in which the satellite is transformed from disky to spheroidal by
tidal forces of the host galaxy. However, we successfully reproduced the
observed Andromeda II kinematics in controlled, self-consistent simulations of
mergers between equal-mass disky dwarf galaxies on a radial or close-to-radial
orbit. In simulations including gas dynamics, star formation and ram pressure
stripping, we are able to reproduce more of the observed properties of
Andromeda II: the unusual rotation, the bimodal star formation history and the
spatial distribution of the two stellar populations, as well as the lack of
gas. We support this scenario by demonstrating the merger origin of prolate
rotation in the cosmological context for sufficiently resolved galaxies in the
Illustris large-scale cosmological hydrodynamical simulation.
