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Galaxy clusters host the largest particle accelerators in the Universe: Shock waves in the intracluster medium (ICM), a hot and ionised plasma, that accelerate particles to high energies. Radio observations pick up synchrotron emission in…

High Energy Astrophysical Phenomena · Physics 2021-02-17 Denis Wittor

Acceleration of cosmic-ray electrons (CRe) in the intra-cluster-medium (ICM) is probed by radio observations that detect diffuse, Mpc-scale, synchrotron sources in a fraction of galaxy clusters. Giant radio halos are the most spectacular…

High Energy Astrophysical Phenomena · Physics 2015-09-11 G. Brunetti

Merging galaxy clusters exhibit strong observational evidence for efficient particle acceleration in the intracluster medium (ICM), particularly in the form of synchrotron-emitting radio relics and halos. Cosmic ray (CR) electrons are…

High Energy Astrophysical Phenomena · Physics 2025-10-29 Rebecca Diesing , Ludwig Böss , Damiano Caprioli

Observations of diffuse radio emission in galaxy clusters indicate that cosmic-ray electrons are accelerated on $\sim$Mpc scales. However, protons appear to be accelerated less efficiently since their associated hadronic $\gamma$-ray…

High Energy Astrophysical Phenomena · Physics 2016-12-14 Denis Wittor , Franco Vazza , Marcus Brüggen

We study the acceleration of cosmic rays by collisionless structure formation shocks with ENZO grid simulations. Data from the FERMI satellite enable the use of galaxy clusters as a testbed for particle acceleration models. Based on…

Astrophysics of Galaxies · Physics 2016-03-23 F. Vazza , M. Brueggen , D. Wittor , C. Gheller , D. Eckert , M. Stubbe

The nonthermal radiation observed from a handfull of clusters of Galaxies is the proof that particle acceleration occurs in the intracluster medium. It is often believed that shock surfaces associated with either mergers of clusters of…

Astrophysics · Physics 2007-05-23 Pasquale Blasi , Stefano Gabici

Galaxy clusters are the largest and most massive gravitationally bound structures known in the Universe. Cosmic-Ray (CR) hadrons accelerated at structure formation shocks and injected by galaxies, are confined in galaxy clusters where they…

High Energy Astrophysical Phenomena · Physics 2019-08-17 Pierre Colin , Fabio Zandanel , Monica Vazquez Acosta , Joaquim Palacio , Christoph Pfrommer , Anders Pinzke

Galaxy clusters grow by gas accretion, mostly from mergers of substructures, which release powerful shock waves into cosmic plasmas and convert a fraction of kinetic energy into thermal energy, amplification of magnetic fields and into the…

High Energy Astrophysical Phenomena · Physics 2019-03-11 A. M. Bykov , F. Vazza , J. A. Kropotina , K. P. Levenfish , F. B. S. Paerels

Weak shocks in the intracluster medium may accelerate cosmic-ray protons and cosmic-ray electrons differently depending on the angle between the upstream magnetic field and the shock normal. In this work, we investigate how shock obliquity…

High Energy Astrophysical Phenomena · Physics 2016-12-07 Denis Wittor , Franco Vazza , Marcus Brüggen

The nonthermal radiation observed from a handfull of clusters of galaxies (CG) is the proof that particle acceleration occurs in the intracluster medium (ICM). It is often believed that shock surfaces associated with either mergers of CG,…

Astrophysics · Physics 2007-05-23 Stefano Gabici

Radio observations prove the existence of relativistic particles and magnetic field associated with the intra-cluster-medium (ICM) through the presence of extended synchrotron emission in the form of radio halos and peripheral relics. This…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 G. Brunetti , T. W. Jones

Particle acceleration is expected to take place at shocks that form during the process of large scale structure formation. Electrons accelerated at such shocks can upscatter a small fraction of the photons in the cosmic microwave background…

Astrophysics · Physics 2007-05-23 Stefano Gabici

Clusters of galaxies are sites of acceleration of charged particles and sources of non-thermal radiation. We report on new constraints on the population of cosmic rays in the Intra Cluster Medium (ICM) obtained via radio observations of a…

Astrophysics · Physics 2009-11-13 G. Brunetti , T. Venturi , D. Dallacasa , R. Cassano , K. Dolag , S. Giacintucci , G. Setti

The nature of cosmic rays (CRs) and cosmic ray transport in galaxy clusters is probed by a number of observations. Radio observations reveal the synchrotron radiation of cosmic ray electrons (CRe) spiraling around cluster magnetic fields.…

High Energy Astrophysical Phenomena · Physics 2019-06-26 Joshua Wiener , Ellen G. Zweibel

We examine the cosmic-ray protons (CRp) accelerated at collisionless shocks in galaxy clusters using cosmological structure formation simulations. We find that in the intracluster medium (ICM) within the virial radius of simulated clusters,…

High Energy Astrophysical Phenomena · Physics 2020-04-08 Ji-Hoon Ha , Dongsu Ryu , Hyesung Kang

We investigate acceleration of cosmic rays by shocks and accretion flows in galaxy clusters. Numerical results for spectra of accelerated particles and nonthermal emission are presented. It is shown that the acceleration of protons and…

High Energy Astrophysical Phenomena · Physics 2019-05-22 V. N. Zirakashvili , V. S. Ptuskin

We investigate the production of cosmic ray (CR) protons at cosmological shocks by performing, for the first time, numerical simulations of large scale structure formation that include directly the acceleration, transport and energy losses…

Astrophysics · Physics 2009-11-06 Francesco Miniati , Dongsu Ryu , Hyesung Kang , T. W. Jones

Although the origin of cosmic rays (CRs) remains an open question, collisionless magnetized shock waves are widely regarded as key sites for particle acceleration. Recent theories further suggest that shock-shock collisions in stellar…

Diffusive shock acceleration is the theory of particle acceleration through multiple shock crossings. In order for this process to proceed at a rate that can be reconciled with observations of high-energy electrons in the vicinity of the…

High Energy Astrophysical Phenomena · Physics 2015-06-04 K. M. Schure , A. R. Bell , L. O'C Drury , A. M. Bykov

Cosmic ray acceleration in turbulent interstellar medium is considered. Turbulence is treated as ensemble of moving magnetic traps. We derive equations for particle momentum distribution function that describes acceleration of particles in…

Astrophysics · Physics 2007-05-23 V. N. Zirakashvili
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