X-ray properties of high-richness CAMIRA clusters in the Hyper Suprime-Cam Subaru Strategic Program field

TL;DR

This study investigates the X-ray properties of 37 high-richness galaxy clusters from the HSC-SSP field, revealing differences in cluster relaxation and luminosity-temperature relations compared to X-ray-selected samples.

Contribution

First X-ray analysis of optically selected high-richness clusters in the HSC-SSP field, providing insights into their morphology and physical state.

Findings

29% of clusters are relaxed based on X-ray peak offsets

Luminosity-temperature relation slope is marginally shallower than X-ray-selected samples

Optical clusters show different X-ray properties, indicating diverse cluster morphologies

Abstract

We present the first results of a pilot X-ray study of 37 rich galaxy clusters at $0.1<z<1.1$ in the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) field. Diffuse X-ray emissions from these clusters were serendipitously detected in the XMM-Newton fields of view. We systematically analyze X-ray images of 37 clusters and emission spectra of a subsample of 17 clusters with high photon statistics by using the XMM-Newton archive data. The frequency distribution of the offset between the X-ray centroid or peak and the position of the brightest cluster galaxy was derived for the optical cluster sample. The fraction of relaxed clusters estimated from the X-ray peak offsets in 17 clusters is $29\pm11(\pm13)$\%, which is smaller than that of the X-ray cluster samples such as HIFLUGCS. Since the optical cluster search is immune to the physical state of X-ray-emitting gas, it is likely to cover a larger range of the cluster morphology. We also derived the luminosity-temperature relation and found that the slope is marginally shallower than those of X-ray-selected samples and consistent with the self-similar model prediction of 2. Accordingly, our results show that the X-ray properties of the optical clusters are marginally different from those observed in the X-ray samples. The implication of the results and future prospects are briefly discussed.