Origin of stellar prolate rotation in a cosmologically simulated faint
  dwarf galaxy
  Stellar prolate rotation in dwarf galaxies is rather uncommon, with only two
known galaxies in the Local Group showing such feature (Phoenix and And II).
Cosmological simulations show that in massive early-type galaxies prolate
rotation likely arises from major mergers. However, the origin of such
kinematics in the dwarf galaxies regime has only been explored using idealized
simulations. Here we made use of hydrodynamical cosmological simulations of
dwarfs galaxies with stellar mass between $3\times10^5$ and $5\times10^8$
M$_{\odot}$ to explore the formation of prolate rotators. Out of $27$ dwarfs,
only one system showed clear rotation around the major axis, whose culprit is a
major merger at $z=1.64$, which caused the transition from an oblate to a
prolate configuration. Interestingly, this galaxy displays a steep metallicity
gradient, reminiscent of the one measured in Phoenix and And II: this is the
outcome of the merger event that dynamically heats old, metal-poor stars, and
of the centrally concentrated residual star formation. Major mergers in dwarf
galaxies offer a viable explanation for the formation of such peculiar systems,
characterized by steep metallicity gradients and prolate rotation.
