Interaction of galactic wind with halo gas and the origin of multiphase
  extraplanar material
  We study the interaction of galactic wind with hot halo gas using
hydrodynamical simulations. We find that the outcome of this interaction
depends crucially on the wind injection density and velocity. Various phases of
the extraplanar media such as high velocity clouds (HVCs), outflowing clouds,
and OVI regions can originate in the interaction zones of wind with the halo
gas, depending on the injection velocity and density. In our simulations the
size of the HVCs is of the order of 100 pc. The total mass contained in the
clouds is 10^5 -- 10^7 M_sun and they have a normal distribution of velocities
in the galactic standard of rest frame, similar to HVCs. For high injection
density and velocity, a significant number of clouds move outwards and resemble
the case of cold neutral outflows. Furthermore a 10^5 -- 10^6 K phase is formed
in our simulations which has a column density ~ 10^{18} cm^{-2}, and resembles
the observed OVI regions. The injection velocity and density are linked with
the mass loading factor of the outflow, efficiency of energy injection due to
supernovae and the SFR. Comparison of the predicted morphology of extraplanar
gas with observations can serve as a useful diagnostic for constraining
feedback efficiency of outflows.
