The mass-concentration relation in massive galaxy clusters at redshift ~1

TL;DR

This study investigates the mass-concentration relation of massive galaxy clusters at redshift 0.8-1.5 using lensing data, revealing a steep dependence on mass and evolutionary trends consistent with theoretical models.

Contribution

It provides the first detailed analysis of the mass-concentration relation at high redshift, highlighting the diversity of cluster dynamical states and their impact on concentration.

Findings

Concentration decreases with increasing mass, c_{200} ~ M_{200}^{-0.83}

High-redshift clusters are less concentrated than local counterparts

Dynamically active clusters tend to have higher concentrations

Abstract

Mass and concentration of clusters of galaxies are related and evolving with redshift. We study the properties of a sample of 31 massive galaxy clusters at high redshift, 0.8 < z < 1.5, using weak and strong lensing observations. Concentration is a steep function of mass, c_{200} ~M_{200}^{-0.83 +-0.39}, with higher-redshift clusters being less concentrated. Mass and concentration from the stacked analysis, M_{200}=(4.1+-0.4)x10^{14}M_Sun/h and c_{200}=2.3+-0.2, are in line with theoretical results extrapolated from the local universe. Clusters with signs of dynamical activity preferentially feature high concentrations. We discuss the possibility that the whole sample is a mix of two different kinds of haloes. Over-concentrated clusters might be accreting haloes out of equilibrium in a transient phase of compression, whereas less concentrated ones might be more relaxed.