MeerKAT view of the diffuse radio sources in Abell 3667 and their interactions with the thermal plasma

TL;DR

This study uses MeerKAT radio observations to provide the most detailed view yet of the complex radio relics, halos, and magnetic interactions in the merging galaxy cluster Abell 3667, revealing filamentary structures and particle acceleration sites.

Contribution

It presents the highest-resolution radio imaging of Abell 3667's relics and halos, linking filamentary structures to particle acceleration and magnetic field enhancements, supported by MHD simulations.

Findings

Filaments show diverse spectral and polarisation properties.

Magnetic field strengths are consistent with unperturbed regions.

Magnetic draping observed around the remnant cool core.

Abstract

During their lifetime, galaxy clusters grow through the accretion of matter from the filaments of the large scale structure and from mergers with other clusters. These mergers release a large amount of energy into the intracluster medium (ICM) through merger shocks and turbulence. These phenomena are associated with the formation of radio sources known as radio relics and radio halos, respectively. Radio relics and halos are unique proxies to study the complex properties of these dynamically active regions of clusters and in general the micro physics of the ICM. Abell 3667 is a spectacular examples of a merging system hosting a large pair of radio relics. Due to its proximity (z=0.0553) and large mass, the system enables the study of these sources to a uniquely high level of detail. We observed Abell 3667 with MeerKAT as part of the MeerKAT Galaxy Cluster Legacy Survey. We used these data to study the large scale emission of the cluster, including its polarisation and spectral properties. We present the most detailed view of the radio relic system in Abell 3667 to date, with a resolution reaching 3 kpc. The relics are filled with a network of filaments with different spectral and polarisation properties that are likely associated with multiple regions of particle acceleration and local enhancements of the magnetic field. Conversely, the magnetic field in the space between filaments has strengths close to that expected in unperturbed regions at the same cluster-centric distance. Comparisons with MHD simulations supports the idea of filaments as multiple acceleration sites. Our observations also confirm the presence of an elongated radio halo, developed in the wake of the bullet-like sub-cluster that merged from the South-East. Finally, we associate the process of magnetic draping to a thin polarised radio source surrounding the remnant of the bullet's cool core.