Dark matter equation of state from rotational curves of galaxies

TL;DR

This paper derives a dark matter equation of state from galaxy rotation curves by modeling halos as non-zero pressure fluids, providing insights into dark matter properties without assuming a barotropic form.

Contribution

It introduces a method to determine the dark matter equation of state directly from observational data, moving beyond traditional zero-pressure models.

Findings

Dark matter halos can be modeled with non-zero pressure equations of state.

Derived equations of state differ from simple barotropic models.

Fitted parameters successfully match observed galaxy rotation curves.

Abstract

In this work we model galactic halos describing the dark matter as a non zero pressure fluid and derive, not impose, a dark matter equation of state by using observational data of the rotation curves of galaxies. In order to reach hydrostatic equilibrium, as expected for the halo, it is mandatory that dark fluid's pressure should not be zero. The equation of state is obtained by solving the matter-geometry system of equations assuming different dark matter density or rotational velocity profiles. The resulting equations of state are, in general, different to a barotropic equation of state. The free parameters of the equation of state are fixed by fitting the observed rotational velocities of a set of galaxies.