Effects of non-vanishing dark matter pressure in the Milky Way galaxy

TL;DR

This paper explores how non-zero pressure in dark matter could influence galactic dynamics, modeling different density profiles and analyzing potential gravitational lensing signatures, thus offering new insights into dark matter properties.

Contribution

It introduces the concept of dark matter with pressure in the Milky Way, compares multiple density profiles, and assesses observational signatures like gravitational lensing.

Findings

Dark matter pressure effects are subtle and hard to distinguish observationally.

Different density profiles produce similar gravitational lensing signatures.

Current observations cannot differentiate between black hole and dark matter distributions in the core.

Abstract

We consider the possibility that the Milky Way's dark matter halo possesses a non vanishing equation of state. Consequently, we evaluate the contribution due to the speed of sound, assuming that the dark matter content of the galaxy behaves like a fluid with pressure. In particular, we model the dark matter distribution via an exponential sphere profile in the galactic core, and inner parts of the galaxy whereas we compare the exponential sphere with three widely-used profiles for the halo, i.e. the Einasto, Burkert and Isothermal profile. For the galactic core we also compare the effects due to a dark matter distribution without black hole with the case of a supermassive black hole in vacuum and show that present observations are unable to distinguish them. Finally we investigate the expected experimental signature provided by gravitational lensing due to the presence of dark matter in the core.