Dynamics of clusters of galaxies in the presence of dark energy: Virgo cluster

TL;DR

The paper investigates whether dark energy–baryon energy exchange can drive expansion of galaxy clusters, challenging the standard virial equilibrium view. It proposes a statistical method to detect radial motions by exploiting brightness-depth effects and applies it to the Virgo cluster using published radial-velocity catalogs and a Dressler density map. Hierarchical clustering reveals subgroups within Virgo that align with density and velocity maxima, suggesting a single system with internal fragmentation. A key result is a positive correlation between subgroups' mean brightness and mean radial velocity, strengthening after removing an outlier, which the authors interpret as evidence of cluster-scale expansion driven by energy transfer from dark energy to baryons.

Abstract

It is shown that, owing to the interaction of baryonic matter with the carrier of dark energy, all configurations of baryonic matter acquire energy and inevitably must expand. This conclusion applies to all hierarchical levels of the baryonic universe, including galaxy clusters. We propose a simple statistical method for identifying possible radial motions of galaxies within clusters. To illustrate this method, we examined the structural features of the Virgo galaxy cluster and identified its substructure, comprising groups of galaxies of varying multiplicity. Galaxies in the substructure are somewhat brighter than those in the overall cluster, and each subgroup contains an active galaxy. Subgroups are considered to be the product of primordial ejections of matter from the central generator galaxy. It is shown that the average stellar magnitude of galaxies in subgroups positively correlates with their average velocity. This correlation can be interpreted as evidence of cluster expansion.