Hydrodynamical Coupling of Mass and Momentum in Multiphase Galactic
  Winds
  Using a set of high resolution hydrodynamical simulations run with the Cholla
code, we investigate how mass and momentum couple to the multiphase components
of galactic winds. The simulations model the interaction between a hot wind
driven by supernova explosions and a cooler, denser cloud of interstellar or
circumgalactic media. By resolving scales of $\Delta x<0.1$ pc over $>100$ pc
distances our calculations capture how the cloud disruption leads to a
distribution of densities and temperatures in the resulting multiphase outflow,
and quantify the mass and momentum associated with each phase. We find the
multiphase wind contains comparable mass and momenta in phases over a wide
range of densities and temperatures extending from the hot wind ($n \approx
10^{-2.5}$ $\mathrm{cm}^{-3}$, $T \approx 10^{6.5}$ K) to the coldest
components ($n \approx 10^2$ $\mathrm{cm}^{-3}$, $T \approx 10^2$ K). We
further find that the momentum distributes roughly in proportion to the mass in
each phase, and the mass-loading of the hot phase by the destruction of cold,
dense material is an efficient process. These results provide new insight into
the physical origin of observed multiphase galactic outflows, and inform galaxy
formation models that include coarser treatments of galactic winds. Our results
confirm that cool gas observed in outflows at large distances from the galaxy
($\gtrsim1$kpc) likely does not originate through the entrainment of cold
material near the central starburst.
