New observational constraints on interacting dark energy using galaxy clusters virial equilibrium states

The nature of the dark sector components of the Universe still remains one of the largest unknown. Among many possibilities, it has been speculated that dark matter and dark energy may be more tightly coupled than usually thought, one component interacting with the other. Here, we continue to explore the possible dark sector interaction through means of the Layzer-Irvine equation together with a model of an interacting dark sector applied to clusters of galaxies. We have selected galaxy clusters that have their mass profiles determined by gravitational lensing effect (optical observations) and have their intracluster gas temperatures measured from X-ray observations and spectral fit found in the literature. Using a simple model based on semi-analytical simulations, we derived a putative dynamical evolution of the clusters and used it to estimate the coupling parameter of the dark sector interaction. Through a Bayesian analysis, we obtain a 3σ detection of the interaction strength for 11 clusters at −0.027 ± 0.009 that translates in a compounded Universal equilibrium virial ratio, U/T, of −0.61+0.04−0.03. We note that the X-ray temperature determination is sometimes inconsistent, depending on the instrument and/or methodology used. The level of detection and these inconsistencies call for caution. We expect that future observations will give us a clearer indication of an eventual dark sector interaction.