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Radio relics are sites of electron (re)acceleration in merging galaxy clusters but the mechanism of acceleration and the topology of the magnetic field in and near relics are yet to be understood. We are carrying out an observational…
Radio relics have been discovered in many galaxy clusters. They are believed to trace shock fronts induced by cluster mergers. Cosmological simulations allow us to study merger shocks in detail since the intra-cluster medium is heated by…
Observations of galaxy clusters show radio emission extended over almost the system scale, necessitating mechanisms for particle acceleration. Previous models for acceleration such as diffusive shock acceleration and that due to turbulence…
We present LOFAR $120-168$ MHz images of the merging galaxy cluster Abell 1240 that hosts double radio relics. In combination with the GMRT $595-629$ MHz and VLA $2-4$ GHz data, we characterised the spectral and polarimetric properties of…
Non-thermal radio emission from cosmic ray electrons in the vicinity of merging galaxy clusters is an important tracer of cluster merger activity, and is the result of complex physical processes that involve magnetic fields, particle…
We investigate binary mergers of galaxy clusters, the formation of shocks, and the resulting radio relics using three-dimensional simulations. The initial setup consists of two idealized spherical subclusters with a mass ratio below three,…
In several merging clusters of galaxies so-called cluster radio relics have been observed. These are extended radio sources which do not seem to be associated with any radio galaxy. Two competing physical mechanisms to accelerate the radio…
Context. It is well-established that shock waves in the intracluster medium launched by galaxy cluster mergers can produce synchrotron emission, which is visible to us at radio frequencies as radio relics. However, the particle acceleration…
High-resolution radio observations of cluster radio relics often show complex spatial and spectral features. However, it is not clear what these features reveal about the underlying magnetic field properties. We performed three-dimensional…
{We simulate the evolution of relativistic electrons injected into the intracluster medium by five radio galaxies. We study the spatial transport and the emission properties of the injected radio plasma over a $\sim 5$ Gyr period, and the…
Radio relics are Mpc-sized synchrotron sources located in the peripheral regions of galaxy clusters. Models based on the diffuse shock acceleration (DSA) scenario have been widely accepted to explain the formation of radio relics. However,…
Galaxy clusters grow by mergers with other clusters and galaxy groups. These mergers create shock waves within the intracluster medium (ICM) that can accelerate particles to extreme energies. In the presence of magnetic fields, relativistic…
Radio relics in galaxy clusters are extended synchrotron sources produced by cosmic-ray electrons in the $\mu$G magnetic field. Many relics are found in the cluster periphery and have a cluster-centric, narrow arc-like shape, which suggests…
Galaxy clusters are the largest gravitationally-bound structures in the Universe. As such, during merger events with similar systems, they release an enormous amount of energy that is dissipated through the formation of shock waves and…
Radio relics could be generated by multiple shocks induced in the turbulent intracluster medium during galaxy mergers. Kang (2021) demonstrated that the re-acceleration of cosmic ray (CR) protons via diffusive shock acceleration (DSA) by…
Observations of large-scale radio emissions prove the existence of shock accelerated cosmic-ray electrons in galaxy clusters, while the lack of detected $\gamma$-rays limits the acceleration of cosmic-ray protons in galaxy clusters. This…
A joint hadronic model is shown to quantitatively explain the observations of diffuse radio emission from galaxy clusters in the form of minihalos, giant halos, relics, and their hybrid, transitional stages. Cosmic-ray diffusion of order…
In this paper we address the question why cluster radio relics that are connected to shock acceleration, so-called radio gischt, have preferentially been found in the outskirts of galaxy clusters. By identifying merger shock waves in…
The Fermi-LAT collaboration recently published deep upper limits to the gamma-ray emission of the Coma cluster, a cluster that hosts the prototype of giant radio halos. In this paper we extend previous studies and use a formalism that…
Diffuse radio emission in galaxy clusters is known to be related to cluster mass and cluster dynamical state. We collect the observed fluxes of radio halos, relics, and mini-halos for a sample of galaxy clusters from the literature, and…