Cosmic ray feedback from supernovae in dwarf galaxies
  The regulation of the baryonic content in dwarf galaxies is a long-standing
problem. Supernovae (SNe) are supposed to play a key role in forming
large-scale galactic winds by removing important amounts of gas from galaxies.
SNe are efficient accelerators of non-thermal particles, so-called cosmic rays
(CRs), which can substantially modify the dynamics of the gas and conditions to
form large-scale galactic winds. We investigate how CR injection by SNe impacts
the star formation and the formation of large-scale winds in dwarf galaxies,
and whether it can produce galaxy star-formation rates (SFR) and wind
properties closer to observations. We ran CR magneto-hydrodynamical simulations
of dwarf galaxies at high resolution (9 pc) with the adaptive mesh refinement
code ramses. Disc galaxies are embedded in isolated halos of mass of $10^{10}$
and $10^{11} \, \rm M_{\odot}$, and CRs are injected by SNe. We included CR
isotropic and anisotropic diffusion with various diffusion coefficients, CR
radiative losses, and CR streaming. The injection of CR energy into the
interstellar medium smooths out the highest gas densities, which reduces the
SFR by a factor of 2-3. Mass outflow rates are significantly greater with CR
diffusion, by 2 orders of magnitudes for the higher diffusion coefficients.
Without diffusion and streaming, CRs are inefficient at generating winds. CR
streaming alone allows for the formation of winds but which are too weak to
match observations. The formation of galactic winds strongly depends on the
diffusion coefficient: for low coefficients, CR energy stays confined in high
density regions where CR energy losses are highest, and higher coefficients,
which allow for a more efficient leaking of CRs out of dense gas, produce
stronger winds. CR diffusion leads to colder and denser winds than without CRs,
and brings outflow rates and mass loading factors much closer to observations.
