A critical analysis of high-redshift, massive galaxy clusters: I

TL;DR

This paper critically assesses statistical tests on high-redshift galaxy clusters to evaluate their consistency with the standard cosmological model, highlighting the importance of survey geometry and selection effects in interpreting results.

Contribution

It provides a detailed comparison of observed high-redshift clusters with simulations, emphasizing the impact of survey geometry and selection functions on statistical consistency.

Findings

Observed clusters are consistent with LCDM when considering existence probabilities.

2d K-S test shows observed clusters are unlikely to be the least probable from simulations.

Adjusting for survey geometry and selection effects can resolve apparent tensions.

Abstract

We critically investigate current statistical tests applied to high redshift clusters of galaxies in order to test the standard cosmological model and describe their range of validity. We carefully compare a sample of high-redshift, massive, galaxy clusters with realistic Poisson sample simulations of the theoretical mass function, which include the effect of Eddington bias. We compare the observations and simulations using the following statistical tests: the distributions of ensemble and individual existence probabilities (in the >M,>z sense), the redshift distributions, and the 2d Kolmogorov-Smirnov test. Using seemingly rare clusters from Hoyle et al. (2011), and Jee et al. (2011) and assuming the same survey geometry as in Jee et al. (2011, which is less conservative than Hoyle et al. 2011), we find that the (>M,>z) existence probabilities of all clusters are fully consistent with LCDM. However assuming the same survey geometry, we use the 2d K-S test probability to show that the observed clusters are not consistent with being the least probable clusters from simulations at >95% confidence, and are also not consistent with being a random selection of clusters, which may be caused by the non-trivial selection function and survey geometry. Tension can be removed if we examine only a X-ray selected sub sample, with simulations performed assuming a modified survey geometry.