Scaling Relations and Overabundance of Massive Clusters at z>~1 from Weak-Lensing Studies with HST

TL;DR

This study uses HST weak-lensing data to analyze high-redshift galaxy clusters, establishing a mass-temperature relation at z>1 and highlighting a tension with the LambdaCDM model due to the overabundance of massive clusters.

Contribution

It presents the first lensing mass-temperature relation at z>1 and assesses the abundance of massive clusters, revealing potential challenges to the standard cosmological model.

Findings

Lensing masses correlate tightly with gas temperatures.

The mass-temperature slope is consistent with self-similar predictions.

The abundance of massive clusters exceeds LambdaCDM expectations.

Abstract

We present weak gravitational lensing analysis of 22 high-redshift (z >~1) clusters based on Hubble Space Telescope images. Most clusters in our sample provide significant lensing signals and are well detected in their reconstructed two-dimensional mass maps. Combining the current results and our previous weak-lensing studies of five other high-z clusters, we compare gravitational lensing masses of these clusters with other observables. We revisit the question whether the presence of the most massive clusters in our sample is in tension with the current LambdaCDM structure formation paradigm. We find that the lensing masses are tightly correlated with the gas temperatures and establish, for the first time, the lensing mass-temperature relation at z >~ 1. For the power law slope of the M-TX relation (M propto T^{\alpha}), we obtain \alpha=1.54 +/- 0.23. This is consistent with the theoretical self-similar prediction \alpha=3/2 and with the results previously reported in the literature for much lower redshift samples. However, our normalization is lower than the previous results by 20-30%, indicating that the normalization in the M-TX relation might evolve. After correcting for Eddington bias and updating the discovery area with a more conservative choice, we find that the existence of the most massive clusters in our sample still provides a tension with the current Lambda CDM model. The combined probability of finding the four most massive clusters in this sample after marginalization over current cosmological parameters is less than 1%.