Production of Cool Gas in Thermally-Driven Outflows
  Galactic outflows commonly contain multiphase gas, and its physical origin
requires explanation. Using the CGOLS (Cholla Galactic OutfLow Simulations)
suite of high-resolution isolated galaxy models, we demonstrate the viability
of rapid radiative cooling as a source of fast-moving ($v \sim 1000$ km/s),
cool ($10^4$ K) gas observed in absorption line studies of outflows around some
star-forming galaxies. By varying the mass-loading and geometry of the
simulated winds, we identify a region of parameter space that leads to cool gas
in outflows. In particular, when using an analytically-motivated central
feedback model, we find that cooling flows can be produced with reasonable
mass-loading rates ($\dot{M}_{wind} / \dot{M}_{SFR} \sim 0.5$), provided the
star formation rate surface density is high. When a more realistic clustered
feedback model is applied, destruction of high density clouds near the disk and
interactions between different outflow regions indicate that lower mass-loading
rates of the hot gas within the feedback region may still produce multiphase
outflows. These results suggest an origin for fast-moving cool gas in outflows
that does not rely on directly accelerating cool gas from the interstellar
medium. These cooling flows may additionally provide an explanation for the
multiphase gas ubiquitously observed in the halos of star-forming galaxies at
low redshift.
