  Galactic-scale winds are a generic feature of massive galaxies with high star
formation rates across a broad range of redshifts. Despite their importance, a
detailed physical understanding of what drives these mass-loaded global flows
has remained elusive. In this paper, we explore the dynamical impact of cosmic
rays by performing the first three-dimensional, adaptive mesh refinement
simulations of an isolated starbursting galaxy that includes a basic model for
the production, dynamics and diffusion of galactic cosmic rays. We find that
including cosmic rays naturally leads to robust, massive, bipolar outflows from
our 10^12 Msun halo, with a mass-loading factor Mout/SFR = 0.3 for our fiducial
run. Other reasonable parameter choices led to mass-loading factors above
unity. The wind is multiphase and is accelerated to velocities well in excess
of the escape velocity. We employ a two-fluid model for the thermal gas and
relativistic CR plasma and model a range of physics relevant to galaxy
formation, including radiative cooling, shocks, self-gravity, star formation,
supernovae feedback into both the thermal and CR gas, and isotropic CR
diffusion. Injecting cosmic rays into star-forming regions can provide
significant pressure support for the interstellar medium, suppressing star
formation and thickening the disk. We find that CR diffusion plays a central
role in driving superwinds, rapidly transferring long-lived CRs from the
highest density regions of the disk to the ISM at large, where their pressure
gradient can smoothly accelerate the gas out of the disk.

Cosmology and Nongalactic Astrophysics