The Galactic fountain as an origin for the Smith Cloud
  The recent discovery of an enriched metallicity for the Smith high-velocity
HI cloud (SC) lends support to a Galactic origin for this system. We use a
dynamical model of the galactic fountain to reproduce the observed properties
of the SC. In our model, fountain clouds are ejected from the region of the
disc spiral arms and move through the halo interacting with a pre-existing hot
corona. We find that a simple model where cold gas outflows vertically from the
Perseus spiral arm reproduces the kinematics and the distance of the SC, but is
in disagreement with the cloud's cometary morphology, if this is produced by
ram-pressure stripping by the ambient gas. To explain the cloud morphology we
explore two scenarios: a) the outflow is inclined with respect to the vertical
direction; b) the cloud is entrained by a fast wind that escapes an underlying
superbubble. Solutions in agreement with all observational constraints can be
found for both cases, the former requires outflow angles >40 deg while the
latter requires >1000 km/s winds. All scenarios predict that the SC is in the
ascending phase of its trajectory and have large - but not implausible - energy
requirements.
