Testing Cosmology with Extreme Galaxy Clusters

TL;DR

This paper uses Extreme Value Statistics to evaluate whether observed galaxy clusters challenge standard cosmological models, finding current observations are consistent with the concordance cosmology when considering full-sky data.

Contribution

It introduces a novel application of Extreme Value Statistics to construct confidence regions in the mass-redshift plane for the most extreme galaxy clusters, aiding in testing cosmological models.

Findings

Observed clusters are consistent with standard cosmology when considering full-sky data.

The mass-redshift diagram can differentiate between cosmological models.

No significant tension found between observations and the concordance model.

Abstract

Motivated by recent suggestions that a number of observed galaxy clusters have masses which are too high for their given redshift to occur naturally in a standard model cosmology, we use Extreme Value Statistics to construct confidence regions in the mass-redshift plane for the most extreme objects expected in the universe. We show how such a diagram not only provides a way of potentially ruling out the concordance cosmology, but also allows us to differentiate between alternative models of enhanced structure formation. We compare our theoretical prediction with observations, placing currently observed high and low redshift clusters on a mass-redshift diagram and find -- provided we consider the full sky to avoid a posteriori selection effects -- that none are in significant tension with concordance cosmology.