Dark matter fluid constraints from galaxy rotation curves

TL;DR

This paper introduces a model-independent method to test if dark matter behaves like a barotropic fluid using galaxy rotation curve data, deriving constraints on its sound speed without assuming specific models.

Contribution

It develops a novel approach to constrain dark matter properties directly from rotation curves, focusing on the fluid's sound speed bounds without relying on specific dark matter models.

Findings

Constraints on the dark matter fluid's sound speed from Milky Way data

Demonstration of the method's potential to test dark matter properties

Discussion of technical challenges and future improvements

Abstract

Galaxy rotation curves are considered to be convincing evidence for dark matter or some dynamically equivalent alternative mechanism. Starting only from the rotation curve data, we present a model independent approach of testing a general hypothesis that dark matter has the properties of a barotropic fluid. It is shown how the speed of sound squared can be expressed in terms of rotation curve data and their radial derivatives and how model independent constraints can be obtained from the requirements that it is confined between 0 and $c^2$. Using the Milky Way rotation curve data available in the literature, we obtain the constraints on the barotropic fluid speed of sound and illustrate the potential of this approach. Technical challenges, limitations and possible future extensions and improvements of the proposed approach are discussed.