Role of cosmic rays in the early stages of galactic outflows
  Using an idealized set-up, we investigate the dynamical role of cosmic rays
(CRs) in the early stages of galactic outflows for galaxies of halo masses
$10^{8}$, $10^{11}$ and $10^{12}$ $M_\odot$. The outflow is launched from a
central region in the galactic disk where we consider three different constant
star formation rates ($0.1$, $1$, and $10$ $M_{\odot}$ yr$^{-1}$) over a
dynamical timescale of $50$ Myr. We determine the temperature distribution of
the gas and find that CRs can reduce the temperature of the shocked gas, which
is consistent with previous results. However, we show that CRs do not have any
noticeable effect on the mass loading by the outflow. We find that CRs can
reduce the size of the outflow, which contradicts previous claims of efficient
dynamical impact of CRs; however, it is consistent with earlier theoretical
models of cosmic ray driven blastwave as well as stellar wind. We discuss the
dependence of our results on CR injection prescriptions and compare them with
earlier studies. We conclude that in the early stages of galactic outflows the
dynamical role of CRs is not important.
