Magnetic fields and relativistic electrons fill entire galaxy cluster

TL;DR

This study uses LOFAR observations to reveal extensive radio synchrotron emission in galaxy cluster Abell 2255, indicating widespread shocks, turbulence, and magnetic fields that influence the cluster's outskirts and contribute to its nonthermal pressure.

Contribution

It provides the first large-scale evidence of pervasive relativistic electrons and magnetic fields filling the entire galaxy cluster, extending to the outskirts.

Findings

Radio emission extends over at least 5 Mpc.

Magnetic field energy density is at least 100 times higher than primordial expectations.

Nonthermal components may significantly contribute to intracluster medium pressure.

Abstract

The hot plasma within merging galaxy clusters is predicted to be filled with shocks and turbulence that may convert part of their kinetic energy into relativistic electrons and magnetic fields generating synchrotron radiation. Analyzing Low Frequency Array (LOFAR) observations of the galaxy cluster Abell 2255, we show evidence of radio synchrotron emission distributed over very large scales of at least 5 megaparsec. The pervasive radio emission witnesses that shocks and turbulence efficiently transfer kinetic energy into relativistic particles and magnetic fields in a region that extends up to the cluster outskirts. The strength of the emission requires a magnetic field energy density at least 100 times higher than expected from a simple compression of primordial fields, presumably implying that dynamo operates efficiently also in the cluster periphery. It also suggests that nonthermal components may contribute substantially to the pressure of the intracluster medium in the cluster periphery.