CHEX-MATE: Morphological analysis of the sample

TL;DR

This study analyzes the X-ray morphology of 118 galaxy clusters from the CHEX-MATE project to classify their dynamical states using morphological parameters and a combined relaxation metric, comparing observations with simulations.

Contribution

It introduces a new combined morphological parameter for continuous classification of galaxy clusters' dynamical states and compares observational data with simulations.

Findings

Morphological parameters are strongly correlated and effectively distinguish relaxed and disturbed clusters.

Sunyaev-Zeldovich clusters tend to be more disturbed than X-ray selected ones.

Simulations generally agree with observations, except for concentration due to AGN feedback effects.

Abstract

In this work, we performed an analysis of the X-ray morphology of the 118 CHEX-MATE (Cluster HEritage project with XMM-Newton - Mass Assembly and Thermodynamics at the Endpoint of structure formation) galaxy clusters, with the aim to provide a classification of their dynamical state. To investigate the link between the X-ray appearance and the dynamical state, we considered four morphological parameters: the surface brightness concentration, the centroid shift, and the second- and third-order power ratios. These indicators result to be: strongly correlated with each other, powerful in identifying the disturbed and relaxed population, characterised by a unimodal distribution and not strongly influenced by systematic uncertainties. In order to obtain a continuous classification of the CHEX-MATE objects, we combined these four parameters in a single quantity, M, which represents the grade of relaxation of a system. On the basis of the M value, we identified the most extreme systems of the sample, finding 15 very relaxed and 27 very disturbed galaxy clusters. From a comparison with previous analysis on X-ray selected samples, we confirmed that the Sunyaev-Zeldovich (SZ) clusters tend to be more disturbed. Finally, by applying our analysis on a simulated sample, we found a general agreement between the observed and simulated results, with the only exception of the concentration. This latter behaviour, is partially related to the presence of particles with high smoothed-particle hydrodynamics density in the central regions of the simulated clusters due to the action of the idealised isotropic thermal Active Galactic Nuclei (AGN) feedback.