An application of extreme value statistics to the most massive galaxy clusters at low and high redshifts

TL;DR

This paper applies general extreme value statistics to analyze the masses of the most massive galaxy clusters at various redshifts, assessing their consistency with the LCDM cosmological model.

Contribution

It introduces a GEV-based framework to evaluate the extremeness of galaxy cluster masses across redshifts, providing new statistical tools for cosmological tests.

Findings

High-redshift clusters are not in tension with LCDM.

No evidence that high-z clusters are more extreme than low-z ones.

Significant conflicts with LCDM require much higher cluster masses.

Abstract

In this work we present an application of general extreme value statistics (GEV) to very massive single clusters at high and low redshifts. After introducing the formalism, we apply this statistics to four very massive high redshift clusters. Those clusters comprise ACT-CL J0102-4915 with a mass of M_200m=(2.16+/-0.32)x10^{15} M_sun at a redshift of z=0.87, SPT-CL J2106-5844 with a mass of M_200m=(1.27+/-0.21)x10^{15} M_sun at z=1.132 and two clusters found by the XMM-Newton Distant Cluster Project survey: XMMU J2235.32557 with a mass of M_200c= (7.3+/-1.3)x10^{14} M_sun located at a redshift of z=1.4 and XMMU J0044.0-2033 having a mass in the range of M_200c= (3.5-5.0)x10^{14} M_sun at z=1.579. By relating those systems to their corresponding distribution functions of being the most massive system in a given survey area, we find that none of the systems alone is in extreme tension with LCDM. We confront these results with a GEV analysis of four very massive low redshift clusters: A2163, A370, RXJ1347-1145 and 1E0657-558, finding no tendency of the high-z systems to be more extreme than the low-z ones. In addition, we study the extreme quantiles of single clusters at high-z and present contour plots for fixed quantiles in the mass vs. survey area plane for four redshift intervals, finding that, in order to be significantly in conflict with LCDM, cluster masses would have to be substantially higher than the currently observed ones.