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류동수

Ryu, Dongsu
Astrophysics Lab.
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Shock acceleration efficiency in radio relics

Author(s)
Botteon, A.Brunetti, G.Ryu, DongsuRoh, S.
Issued Date
2020-02
DOI
10.1051/0004-6361/201936216
URI
https://scholarworks.unist.ac.kr/handle/201301/31556
Fulltext
https://www.aanda.org/articles/aa/abs/2020/02/aa36216-19/aa36216-19.html
Citation
ASTRONOMY & ASTROPHYSICS, v.634, pp.A64
Abstract
Context. 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 mechanisms leading to the formation of relativistic particles in this environment are still not well understood.

Aims. The diffusive shock acceleration (DSA) theory is a commonly adopted scenario to explain the origin of cosmic rays at astrophysical shocks, including those in radio relics in galaxy clusters. However, in a few specific cases it has been shown that the energy dissipated by cluster shocks is not enough to reproduce the luminosity of the relics via DSA of thermal particles. Studies based on samples of radio relics are required to further address this limitation of the mechanism.

Methods. In this paper, we focus on ten well-studied radio relics with underlying shocks observed in the X-rays and calculate the electron acceleration efficiency of these shocks that is necessary to reproduce the observed radio luminosity of the relics.

Results. We find that in general the standard DSA cannot explain the origin of the relics if electrons are accelerated from the thermal pool with an efficiency significantly smaller than 10%. Our results show that other mechanisms, such as shock re-acceleration of supra-thermal seed electrons or a modification of standard DSA, are required to explain the formation of radio relics.
Publisher
EDP SCIENCES S A
ISSN
0004-6361
Keyword (Author)
acceleration of particlesradiation mechanismsnon-thermalthermalgalaxiesclustersintracluster mediumgeneralshock waves
Keyword
PARTICLE-ACCELERATIONGALAXY CLUSTERSBULLET CLUSTERABELL 3376EMISSIONHALOORIGINTELESCOPEELECTRONFRONTS

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