XMM-Newton observations of ten high-redshift CAMIRA clusters of galaxies

TL;DR

This study uses XMM-Newton data to analyze ten high-redshift galaxy clusters from the CAMIRA catalog, revealing their dynamical states, scaling relations, and increased AGN activity, which inform models of cluster formation and evolution.

Contribution

It provides the first detailed X-ray analysis of high-redshift CAMIRA clusters, establishing their scaling relations and dynamical states, and linking AGN activity to cluster assembly.

Findings

Only one cluster is dynamically relaxed, indicating a low relaxed fraction at high redshift.

Scaling relations are consistent with self-similar and baseline models, with no significant redshift evolution.

High AGN activity in outskirts suggests enhanced triggering during early cluster formation.

Abstract

We present results from XMM-Newton observations of ten high-redshift ($0.81 < z < 1.17$) galaxy clusters selected from the CAMIRA catalog based on high richness ($N > 40$). These massive clusters, identified in the Hyper Suprime-Cam Subaru Strategic Program field, provide an ideal sample for probing the dynamical state of the intracluster medium (ICM) in the early Universe. We performed uniform X-ray imaging and spectral analyses to measure the ICM temperature and bolometric luminosity, and investigated cluster morphology through offsets between the brightest cluster galaxy (BCG) and the X-ray peak. Extended X-ray emission was detected from all targets, but only one system was classified as dynamically relaxed, indicating a low relaxed fraction ($\sim 10\%$) at high redshift. By combining this high-$z$ sample with a lower-redshift CAMIRA cluster sample, we derived scaling relations among richness, temperature, luminosity, and mass. The results are broadly consistent with predictions from both the self-similar model and the baseline model incorporating the mass--concentration relation. We find no significant redshift evolution, strengthening the view that cluster scaling relations are largely established by $z \sim 1$. We also examined the AGN fraction among member galaxies and found significantly higher AGN activity in high-redshift clusters, particularly in the outskirts, suggesting enhanced AGN triggering during early cluster assembly and a possible connection to the thermodynamic state of dynamically young clusters. These findings provide new insights into the formation and evolution of massive clusters and the thermodynamic history of the ICM, and complement large-area X-ray surveys such as eROSITA.