Non-virialised clusters for detection of Dark Energy-Dark Matter interaction

TL;DR

This study explores whether deviations from virial equilibrium in galaxy clusters can reveal interactions between dark matter and dark energy, using observational data and a simple interacting dark sector model.

Contribution

It applies a modified virial analysis to observational data to assess dark sector interactions, providing a novel approach to detect dark energy-dark matter coupling.

Findings

Cluster out of equilibrium confirmed

Interaction strength compatible with no interaction

Potential 2σ detection of dark sector interaction

Abstract

The observation of galaxy and gas distributions, as well as cosmological simulations in a $\Lambda$CDM Universe, suggests that clusters of galaxies are still accreting mass and are not expected to be in equilibrium. In this work, we investigate the possibility to evaluate the departure from virial equilibrium in order to detect, in that balance, effects from a Dark Matter--Dark Energy interaction. We continue, from previous works, using a simple model of interacting dark sector, the Layzer--Irvine equation for dynamical virial evolution, and employ optical observations in order to obtain the mass profiles through weak lensing and X-ray observations giving the intracluster gas temperatures. Through a Monte Carlo method, we generate, for a set of clusters, measurements of observed virial ratios, interaction strength, rest virial ratio and departure from equilibrium factors. We found a compounded interaction strength of $-1.99^{+2.56}_{-16.00}$, compatible with no interaction, but also a compounded rest virial ratio of $-0.79 \pm 0.13$, which would entail a $2\sigma$ detection. We confirm quantitatively that clusters of galaxies are out of equilibrium but further investigation is needed to constrain a possible interaction in the dark sector.