Testing the Bose-Einstein Condensate dark matter model at galactic cluster scale

TL;DR

This paper extends the Bose-Einstein Condensate dark matter model to galaxy clusters, deriving density profiles and fitting observational data to constrain dark matter particle properties at the cluster scale.

Contribution

It develops a theoretical framework for BEC dark matter in galaxy clusters, incorporating hydrostatic equilibrium and hot gas models, and compares predictions with observational data.

Findings

Dark matter particle mass around micro-eV scale

Scattering length estimated near 10^{-7} fm

Upper bounds on particle properties from cluster data

Abstract

The possibility that dark matter may be in the form of a Bose-Einstein Condensate (BEC) has been extensively explored at galactic scale. In particular, good fits for the galactic rotations curves have been obtained, and upper limits for the dark matter particle mass and scattering length have been estimated. In the present paper we extend the investigation of the properties of the BEC dark matter to the galactic cluster scale, involving dark matter dominated astrophysical systems formed of thousands of galaxies each. By considering that one of the major components of a galactic cluster, the intra-cluster hot gas, is described by King's $\beta$-model, and that both intra-cluster gas and dark matter are in hydrostatic equilibrium, bound by the same total mass profile, we derive the mass and density profiles of the BEC dark matter. In our analysis we consider several theoretical models, corresponding to isothermal hot gas and zero temperature BEC dark matter, non-isothermal gas and zero temperature dark matter, and isothermal gas and finite temperature BEC, respectively. The properties of the finite temperature BEC dark matter cluster are investigated in detail numerically. We compare our theoretical results with the observational data of 106 galactic clusters. Using a least-squares fitting, as well as the observational results for the dark matter self-interaction cross section, we obtain some upper bounds for the mass and scattering length of the dark matter particle. Our results suggest that the mass of the dark matter particle is of the order of $\mu $eV, while the scattering length has values in the range of $10^{-7}$ fm.