A hydrodynamical study of outflows in starburst galaxies with different
  driving mechanisms
  Outflows from starburst galaxies can be driven by thermal pressure, radiation
and cosmic rays. We present an analytic phenomenological model that accounts
for these contributions simultaneously to investigate their effects on the
hydrodynamical properties of outflows. We assess the impact of energy
injection, wind opacity, magnetic field strength and the mass of the host
galaxy on flow velocity, temperature, density and pressure profiles. For an
M82-like wind, a thermally-dominated driving mechanism is found to deliver the
fastest and hottest wind. Radiation-driven winds in typical starburst-galaxy
configurations are unable to attain the higher flow velocities and temperatures
associated with thermal and cosmic ray-driven systems, leading to higher wind
densities which would be more susceptible to cooling and fragmentation at lower
altitudes. High opacity winds are more sensitive to radiative driving, but
terminal flow velocities are still lower than those achieved by other driving
mechanisms at realistic opacities. We demonstrate that variations in the
outflow magnetic field can influence its coupling with cosmic rays, where
stronger fields enable greater streaming but less driving near the base of the
flow, instead with cosmic rays redirecting their driving impact to higher
altitudes. The gravitational potential is less important in M82-like wind
configurations, and substantial variations in the flow profiles only emerge at
high altitude in massive haloes. This model offers a more generalised approach
to examine the large scale hydrodynamical properties for a wide variety of
starburst galaxies.
