Dissipative dark matter halos: The steady state solution

TL;DR

This paper models the steady state configurations of dissipative dark matter halos influenced by heating from supernovae and cooling processes, finding that mirror dark matter models struggle to produce realistic halos under certain assumptions.

Contribution

It provides a numerical analysis of steady state solutions for dissipative dark matter halos, highlighting challenges in mirror dark matter models and exploring more generic scenarios.

Findings

Mirror dark matter halos face difficulties achieving realistic steady states.

Cooling processes often dominate over heating in the models considered.

More generic dissipative dark matter models can potentially resolve the issues identified.

Abstract

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.