A radio ridge connecting two galaxy clusters in a filament of the cosmic web

TL;DR

This paper reports the discovery of a radio-emitting filament connecting two galaxy clusters, suggesting re-acceleration of particles by weak shocks in the cosmic web's filamentary structure.

Contribution

It presents the first observation of a radio ridge linking galaxy clusters and demonstrates the role of weak shocks in particle re-acceleration within cosmic filaments.

Findings

Radio emission connects galaxy clusters Abell 0399 and Abell 0401.

Weak shocks can re-accelerate relativistic particles in cosmic filaments.

Magnetic fields and relativistic electrons are present in the filament.

Abstract

Galaxy clusters are the most massive gravitationally bound structures in the Universe. They grow by accreting smaller structures in a merging process that produces shocks and turbulence in the intra-cluster gas. We observed a ridge of radio emission connecting the merging galaxy clusters Abell 0399 and Abell 0401 with the Low Frequency Array (LOFAR) at 140 MHz. This emission requires a population of relativistic electrons and a magnetic field located in a filament between the two galaxy clusters. We performed simulations to show that a volume-filling distribution of weak shocks may re-accelerate a pre-existing population of relativistic particles, producing emission at radio wavelengths that illuminates the magnetic ridge.