Cosmological cluster tension

TL;DR

This paper reviews the tension between observed galaxy cluster abundance and LCDM model predictions, exploring potential solutions like massive neutrinos, modified gravity, and biases in measurements.

Contribution

It provides an updated analysis of cluster abundance tension and evaluates the likelihood of various proposed solutions.

Findings

Tension exists between cluster observations and LCDM predictions.

Massive neutrinos and modified gravity could alleviate the tension.

Biases in selection or mass calibration are also considered as explanations.

Abstract

The abundance of clusters is a classical cosmological probe sensitive to both the geometrical aspects and the growth rate of structures. The abundance of clusters of galaxies measured by Planck has been found to be in tension with the prediction of the LCDM models normalized to Planck CMB fluctuations power spectra. The same tension appears with X-ray cluster local abundance. Massive neutrinos and modified gravity are two possible solutions to fix this tension. Alternatively, others options include a bias in the selection procedure or in the mass calibration of clusters. We present a study, based on our recent work, updating the present situation on this topic and discuss the likelihood of the various options.