Probing the Large-Scale Structure Around the Most Distant Galaxy Clusters from the Massive Cluster Survey

TL;DR

This study maps the large-scale structure around twelve distant galaxy clusters from MACS, revealing filaments, satellite clusters, and gas-galaxy offsets indicative of ongoing mergers, supporting models of cluster growth via filamentary accretion.

Contribution

It provides detailed wide-field maps of the cosmic environment around high-redshift clusters, directly observing filaments and satellite systems, and compares galaxy and gas distributions to study cluster dynamics.

Findings

Detection of satellite clusters and filaments around most studied clusters.

Identification of offsets between gas and galaxy distributions indicating mergers.

Filaments are promising targets for studying the warm-hot intergalactic medium.

Abstract

We present maps of the cosmic large-scale structure around the twelve most distant galaxy clusters from the Massive Cluster Survey (MACS) as traced by the projected surface density of galaxies on the cluster red sequence. Taken with the Suprime-Cam wide-field camera on the Subaru telescope, the images used in this study cover a 27x27 arcmin^2 area around each cluster, corresponding to 10 x 10 Mpc^2 at the median redshift of z = 0.55 of our sample. We directly detect satellite clusters and filaments extending over the full size of our imaging data in the majority of the clusters studied, supporting the picture of mass accretion via infall along filaments suggested by numerical simulations of the growth of clusters and the evolution of large-scale structure. A comparison of the galaxy distribution near the cluster cores with the X-ray surface brightness as observed with Chandra reveals, in several cases, significant offsets between the gas and galaxy distribution, indicative of ongoing merger events. The respective systems are ideally suited for studies of the dynamical properties of gas, galaxies, and dark matter. In addition, the large-scale filaments viewed at high contrast in these MACS clusters are prime targets for the direct detection and study of the warm-hot intergalactic medium (WHIM).