Abstract
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 extending from the hot wind $(n 10^-3$
$cm^-3)$ to the coldest components $(n 10^2$
$cm^-3)$. 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.
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