Dissipative dark matter halos: The steady state solution
  Dissipative dark matter, where dark matter particle properties closely
resemble familiar baryonic matter, is considered. Mirror dark matter, which
arises from an isomorphic hidden sector, is a specific and theoretically
constrained scenario. Other possibilities include models with more generic
hidden sectors that contain massless dark photons (unbroken $U(1)$ gauge
interactions). Such dark matter not only features dissipative cooling
processes, but is also assumed to have nontrivial heating sourced by ordinary
supernovae (facilitated by the kinetic mixing interaction). The dynamics of
dissipative dark matter halos around rotationally supported galaxies,
influenced by heating as well as cooling processes, can be modelled by fluid
equations. For a sufficiently isolated galaxy with stable star formation rate,
the dissipative dark matter halos are expected to evolve to a steady state
configuration which is in hydrostatic equilibrium and where heating and cooling
rates locally balance. Here, we take into account the major cooling and heating
processes, and numerically solve for the steady state solution under the
assumptions of spherical symmetry, negligible dark magnetic fields, and that
supernova sourced energy is transported to the halo via dark radiation. For the
parameters considered, and assumptions made, we were unable to find a
physically realistic solution for the constrained case of mirror dark matter
halos. Halo cooling generally exceeds heating at realistic halo mass densities.
This problem can be rectified in more generic dissipative dark matter models,
and we discuss a specific example in some detail.
