Cosmic Ray Driven Outflows in an Ultraluminous Galaxy
  In models of galaxy formation, feedback driven both by supernova (SN) and
active galactic nucleus (AGN) is not efficient enough to quench star formation
in massive galaxies. Models of smaller galaxies have suggested that cosmic rays
(CRs) play a major role in expelling material from the star forming regions by
diffusing SN energy to the lower density outskirts. We therefore run gas
dynamical simulations of galactic outflows from a galaxy contained in a halo
with $5\times10^{12}$~M$_{\odot}$ that resembles a local ultraluminous galaxy,
including both SN thermal energy and a treatment of CRs using the same
diffusion approximation as Salem & Bryan. We find that CR pressure drives a
low-density bubble beyond the edge of the shell swept up by thermal pressure,
but the main bubble driven by SN thermal pressure overtakes it later, which
creates a large-scale biconical outflow. CRs diffusing into the disk are unable
to entrain its gas in the outflows, yielding a mass-loading rate of only
$\sim0.1~\%$ with varied CR diffusion coefficients. We find no significant
difference in mass-loading rates in SN driven outflows with or without CR
pressure. Our simulations strongly suggest that it is hard to drive a heavily
mass-loaded outflow with CRs from a massive halo potential, although more
distributed star formation could lead to a different result.
