Hydrodynamical description of Galactic Dark Matter

TL;DR

This paper models galactic dark matter halos as self-gravitating, self-interacting gases within General Relativity, linking empirical rotation curves to particle properties and constraining dark matter particle masses.

Contribution

It introduces a hydrodynamical, relativistic model of galactic dark matter halos consistent with observed rotation curves and derives bounds on particle masses.

Findings

Compatibility with universal rotation curves

Mass bounds for dark matter particles between 30 eV and 60 eV

Includes candidates like neutralino, axino, and lighter particles

Abstract

We consider simple hydrodynamical models of galactic dark matter in which the galactic halo is a self-gravitating and self-interacting gas that dominates the dynamics of the galaxy. Modeling this halo as a sphericaly symmetric and static perfect fluid satisfying the field equations of General Relativity, visible barionic matter can be treated as ``test particles'' in the geometry of this field. We show that the assumption of an empirical ``universal rotation curve'' that fits a wide variety of galaxies is compatible, under suitable approximations, with state variables characteristic of a non-relativistic Maxwell-Boltzmann gas that becomes an isothermal sphere in the Newtonian limit. Consistency criteria lead to a minimal bound for particle masses in the range $30 \hbox{eV} \alt m \alt 60 \hbox{eV}$ and to a constraint between the central temperature and the particles mass. The allowed mass range includes popular supersymmetric particle candidates, such as the neutralino, axino and gravitino, as well as lighter particles ($m\sim$ keV) proposed by numerical N-body simulations associated with self-interactive ``cold'' and ``warm'' dark matter structure formation theories.