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Radio relics in galaxy clusters are associated with powerful shocks that (re)accelerate relativistic electrons. It is widely believed that the acceleration proceeds via diffusive shock acceleration. In the framework of thermal leakage, the…

High Energy Astrophysical Phenomena · Physics 2015-05-13 F. Vazza , D. Eckert , M. Brueggen , B. Huber

Recent radio observations have identified a class of structures, so-called radio relics, in clusters of galaxies. The radio emission from these sources is interpreted as synchrotron radiation from GeV electrons gyrating in microG-level…

High Energy Astrophysical Phenomena · Physics 2015-06-05 Hyesung Kang , Dongsu Ryu , T. W. Jones

The acceleration of electrons at shock fronts is thought to be responsible for radio relics, extended radio features in the vicinity of merging galaxy clusters. By combining high resolution Adaptive Mesh Refinement Hydro/N-body cosmological…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-17 Jack O. Burns , Samuel W. Skillman

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,…

High Energy Astrophysical Phenomena · Physics 2026-05-27 Hyesung Kang , Dongsu Ryu , Jeongbhin Seo

X-ray shocks and radio relics detected in the cluster outskirts are commonly interpreted as shocks induced by mergers of sub-clumps. We study the properties of merger shocks in merging galaxy clusters, using a set of cosmological…

Cosmology and Nongalactic Astrophysics · Physics 2018-04-25 Ji-Hoon Ha , Dongsu Ryu , Hyesung Kang

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

Radio relics detected in the outskirts of galaxy clusters are thought to trace radio-emitting relativistic electrons accelerated at cosmological shocks. In this study, using the cosmological hydrodynamic simulation data for the large-scale…

High Energy Astrophysical Phenomena · Physics 2015-10-14 Sungwook E. Hong , Hyesung Kang , Dongsu Ryu

Many bright radio relics in the outskirts of galaxy clusters have low inferred Mach numbers, defying expectations from shock acceleration theory and heliospheric observations that the injection efficiency of relativistic particles plummets…

Cosmology and Nongalactic Astrophysics · Physics 2013-09-03 Anders Pinzke , S. Peng Oh , Christoph Pfrommer

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

Cosmological shocks are a critical part of large-scale structure formation, and are responsible for heating the intracluster medium in galaxy clusters. In addition, they are also capable of accelerating non-thermal electrons and protons. In…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-19 Samuel W. Skillman , Eric J. Hallman , Brian W. O'Shea , Jack O. Burns , Britton D. Smith , Matthew J. Turk

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…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-13 M. Hoeft , S. E. Nuza , S. Gottloeber , R. J. van Weeren , H. J. A. Roettgering , M. Brueggen

Radio relics associated with merging galaxy clusters indicate the acceleration of relativistic electrons in merger-driven shocks with low sonic Mach numbers ($M_{\rm s}\lesssim 3$) in the intracluster medium (ICM). Recent studies have…

High Energy Astrophysical Phenomena · Physics 2021-07-07 Ji-Hoon Ha , Sunjung Kim , Dongsu Ryu , Hyesung Kang

On the largest scales, the Universe consists of voids and filaments making up the cosmic web. Galaxy clusters are located at the knots in this web, at the intersection of filaments. Clusters grow through accretion from these large-scale…

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…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Samuel W. Skillman , Hao Xu , Eric J. Hallman , Brian W. O'Shea , Jack O. Burns , Hui Li , David C. Collins , Michael L. Norman

This study investigates the impact of magnetic turbulence on cosmic ray (CR) electrons through Fermi-II acceleration behind merger-driven shocks in the intracluster medium and examines how the ensuing synchrotron radio emission is…

High Energy Astrophysical Phenomena · Physics 2024-05-07 Hyesung Kang

Radio relics in galaxy clusters are giant diffuse synchrotron sources powered in cluster outskirts by merger shocks. Although the relic-shock connection has been consolidated in recent years by a number of observations, the details of the…

High Energy Astrophysical Phenomena · Physics 2020-02-12 A. Botteon , G. Brunetti , D. Ryu , S. Roh

It is generally accepted that radio relics are the result of synchrotron emission from shock-accelerated electrons. Current models, however, are still unable to explain several aspects of their formation. In this paper, we focus on three…

High Energy Astrophysical Phenomena · Physics 2026-02-02 Joseph Whittingham , Christoph Pfrommer , Maria Werhahn , Léna Jlassi , Philipp Girichidis

In the course of the formation of cosmological structures, large shock waves are generated in the intra-cluster medium. In analogy to processes in supernova remnants, these shock waves may generate a significant population of relativistic…

Astrophysics · Physics 2008-11-26 Matthias Hoeft , Marcus Brueggen

Galaxy clusters are known to host many active galaxies (AGNs) with radio jets, which could expand to form radio bubbles with relativistic electrons in the intracluster medium (ICM). It has been suggested that fossil relativistic electrons…

High Energy Astrophysical Phenomena · Physics 2019-01-09 Hyesung Kang

Cosmology models predict that external accretion shocks form in the outer region of galaxy clusters due to supersonic gas infall from filaments and voids in the cosmic web. They are characterized by high sonic and Alfv\'enic Mach numbers,…

High Energy Astrophysical Phenomena · Physics 2023-02-08 Ji-Hoon Ha , Dongsu Ryu , Hyesung Kang
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