Kinetic energy from supernova feedback in high-resolution galaxy
  simulations
  We describe a new method for adding a prescribed amount of kinetic energy to
simulated gas modeled on a cartesian grid by directly altering grid cells' mass
and velocity in a distributed fashion. The method is explored in the context of
supernova feedback in high-resolution ($\sim 10$ pc) hydrodynamic simulations
of galaxy formation. Resolution-dependence is a primary consideration in our
application of the method and simulations of isolated explosions (performed at
different resolutions) motivate a resolution-dependent scaling for the injected
fraction of kinetic energy that we apply in cosmological simulations of a
$10^9$ Msun dwarf halo. We find that in high density media ($\gtrsim$ 50
cm$^{-3}$) with coarse resolution ($\gtrsim 4$ pc per cell), results are
sensitive to the initial kinetic energy fraction due to early and rapid
cooling. In our galaxy simulations, the deposition of small amounts of
supernova energy in kinetic form (as little as 1%) has a dramatic impact on the
evolution of the system, resulting in an order of magnitude suppression of
stellar mass. The overall behavior of the galaxy in the two highest resolution
simulations we perform appears to converge. We discuss the resulting
distribution of stellar metallicities, an observable sensitive to galactic wind
properties, and find that while the new method demonstrates increased agreement
with observed systems, significant discrepancies remain, likely due to
simplistic assumptions that neglect contributions from Type Ia supernovae and
stellar winds.
