The density of virialized clusters as a probe of dark energy

TL;DR

This paper demonstrates that the average density of virialized galaxy clusters depends on dark energy properties and gravity, proposing it as a new probe to test cosmological models, especially those addressing current tensions.

Contribution

It introduces a method using the spherical collapse model to relate cluster densities to dark energy parameters, including negative cosmological constants, expanding the scope of cosmological probes.

Findings

Virialized cluster density depends on dark energy and gravity.

Negative cosmological constant models can amplify cluster densities by up to 80%.

Implications for early galaxy formation and JWST observations.

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 $\Omega_{\Lambda,0}=-0.7$ (with $\Omega_{m,0}=0.3$) preferred by $\Lambda$ sign-switching models ($\Lambda_s\text{CDM}$) proposed for the resolution of the Hubble and $S_8$ tensions, we find an amplification of the density of virialized clusters which can be as large as $80\%$ compared to \plcdm for a turnaround redshift $z_{\text{max}} \gtrsim 2$. Such an amplification may lead to more efficient early galaxy formation in this class of models in accordance with the recent findings of JWST.