The density of virialized clusters as a probe of dark energy

Abstract

We use the spherical collapse model to demonstrate that the observable average density of virialized clusters depends on the properties of dark energy along with the properties of gravity on cluster scales and can therefore be used as a probe of these properties. As an application of this approach we derive the predicted virialized densities and radii of cluster mass structures for a wide range of values of the cosmological constant (including negative values) as a function of the turnaround redshift. For the value of ΩΛ, 0 = −0.7 (with Ωm, 0 = 0.3), we find an amplification of the density of virialized clusters which can be as large as 80% compared to Planck18/ΛCDM for a turnaround redshift zmax ≳ 2. Such an amplification may lead to more efficient early galaxy formation in this class of models, in accordance with the recent findings of JWST, which may be partially pertinent to the Λ sign-switching models (ΛsCDM), which have been suggested as potential solutions to the observed Hubble and S8 discrepancies.