Related papers: Do radio relics challenge diffusive shock accelera…
The thermal plasma of galaxy clusters lost most of its information on how structure formation proceeded as a result of dissipative processes. In contrast, non-equilibrium distributions of cosmic rays (CR) preserve the information about…
Large-scale diffuse radio emission is observed in some clusters of galaxies. There is ample of evidence that the emission has its origin in synchrotron losses of relativistic electrons, accelerated in the course of clusters mergers. In a…
We review observations of extended regions of radio emission in clusters; these include diffuse emission in `relics', and the large central regions commonly referred to as `halos'. The spectral observations, as well as Faraday rotation…
Recent results on the radio emission from galaxy clusters are reviewed, with emphasis both on the radio galaxies and on the diffuse radio emission from the intracluster medium. We show that the formation of the tailed morphology in cluster…
We give for a plasma with a history of several expansion and contraction phases an analytical model of the evolution of a contained relativistic electron population under synchrotron, inverse Compton and adiabatic energy losses or gains.…
A very important aspect of the radio emission from galaxy clusters is represented by the diffuse radio sources associated with the intracluster medium: radio halos and relics. These radio sources indicate the existence of large scale…
Recent radio observations support a picture for star formation where there is accretion of matter onto a central protostar with the ejection of molecular outflows that can affect the surrounding medium. The impact of a supersonic outflow on…
Context. The recent discovery of so-called mega radio halos as a new class of diffuse, steep-spectrum radio sources in clusters of galaxies has raised questions about the origin and the evolution of cluster-wide radio emission. Aims. We…
We discuss the recent developments in the theory of diffusive shock acceleration (DSA) by using both first-principle kinetic plasma simulations and analytical theory based on the solution of the convection/diffusion equation. In particular,…
All galaxies without a radio-loud AGN follow a tight correlation between their global FIR and radio synchrotron luminosities, which is believed to be ultimately the result of the formation of massive stars. Two face-on colliding pairs of…
Galaxy clusters are considered to be gigantic reservoirs of cosmic rays (CRs). Some of the clusters are found with extended radio emission, which provides evidence for the existence of magnetic fields and CR electrons in the intra-cluster…
Diffusive Shock Acceleration (DSA) cannot efficiently accelerate particles without the presence of self-consistently generated or pre-existing strong turbulence ($ \delta B/B \sim 1 $) in the vicinity of the shock. The problem we address in…
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…
There is a growing evidence that extended radio halos are most likely generated by electrons reaccelerated via some kind of turbulence generated in the cluster volume during major mergers. It is well known that Alfv\'en waves channel most…
Although radio relics are understood to originate in intracluster shock waves resulting from merger shocks, the most widely used model for describing this (re-)acceleration process at shock fronts, the diffusive shock acceleration (DSA)…
We developed a magneto-turbulent model for the cosmic ray (CR) electrons seen in the radio halo clusters of galaxies. Steady state momentum distribution functions of the CR electrons are calculated for given spectra of the turbulent Alfven…
Accretion of gas onto already virialized structures like galaxy clusters should give rise to accretion shocks which can potentially accelerate cosmic rays. Here, we use the radio emission detected from Coma cluster and models of evolution…
Recent improvements in the capabilities of low frequency radio telescopes provide a unique opportunity to study thermal and non-thermal properties of the cosmic web. We argue that the diffuse, polarized emission from giant radio relics…
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…
We study the evolution of the energy spectrum of cosmic-ray electrons accelerated at spherically expanding shocks with low Mach numbers and the ensuing spectral signatures imprinted in radio synchrotron emission. Time-dependent simulations…