# Diffuse Radio Emission from Galaxy Clusters

## TL;DR

This paper reviews the properties and recent observational findings of diffuse radio sources in galaxy clusters, discussing their classifications, physical processes, and implications for intracluster medium physics, including cosmic web emission detection.

## Contribution

It provides a comprehensive overview of diffuse cluster radio sources, including recent observational results and an updated catalog, highlighting advances in understanding ICM magnetic fields and acceleration processes.

## Key findings

- Diffuse radio sources reveal cosmic rays and magnetic fields in ICM.
- Classification of sources into halos, relics, and revived fossil plasma.
- Recent observational data support models of shock acceleration and fossil plasma revival.

## Abstract

In a growing number of galaxy clusters diffuse extended radio sources have been found. These sources are not directly associated with individual cluster galaxies. The radio emission reveal the presence of cosmic rays and magnetic fields in the intracluster medium (ICM). We classify diffuse cluster radio sources into radio halos, cluster radio shocks (relics), and revived AGN fossil plasma sources. Radio halo sources can be further divided into giant halos, mini-halos, and possible `intermediate' sources. Halos are generally positioned at cluster center and their brightness approximately follows the distribution of the thermal ICM. Cluster radio shocks (relics) are polarized sources mostly found in the cluster's periphery. They trace merger induced shock waves. Revived fossil plasma sources are characterized by their radio steep-spectra and often irregular morphologies. In this review we give an overview of the properties of diffuse cluster radio sources, with an emphasis on recent observational results. We discuss the resulting implications for the underlying physical acceleration processes that operate in the ICM, the role of relativistic fossil plasma, and the properties of ICM shocks and magnetic fields. We also compile an updated list of diffuse cluster radio sources which will be available on-line http://galaxyclusters.com. We end this review with a discussion on the detection of diffuse radio emission from the cosmic web.