X-Ray morphological analysis of the Planck ESZ clusters

TL;DR

This study analyzes the morphology of galaxy clusters from the Planck ESZ sample using X-ray data, identifying key parameters that distinguish relaxed from disturbed systems and confirming their disturbed nature compared to other samples.

Contribution

It introduces a set of morphological parameters to classify cluster dynamical states and compares the disturbance levels of Planck ESZ clusters with other samples.

Findings

Concentration and centroid-shift are effective in classifying cluster relaxation states.

No correlation between cluster mass and dynamical state.

ESZ clusters are generally more disturbed than X-ray selected samples.

Abstract

X-ray observations show that galaxy clusters have a very large range of morphologies. The most disturbed systems which are good to study how clusters form and grow and to test physical models, may potentially complicate cosmological studies because the cluster mass determination becomes more challenging. Thus, we need to understand the cluster properties of our samples to reduce possible biases. This is complicated by the fact that different experiments may detect different cluster populations. For example, SZ selected cluster samples have been found to include a greater fraction of disturbed systems than X-ray selected samples. In this paper we determined eight morphological parameters for the Planck Early Sunyaev-Zeldovich (ESZ) objects observed with XMM-Newton. We found that two parameters, concentration and centroid-shift, are the best to distinguish between relaxed and disturbed systems. For each parameter we provide the values that allow one to select the most relaxed or most disturbed objects from a sample. We found that there is no mass dependence on the cluster dynamical state. By comparing our results with what was obtained with REXCESS clusters, we also confirm that indeed the ESZ clusters tend to be more disturbed, as found by previous studies.