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Galaxies 2016, 4(4), 68;

Relic—Shock Connection in Abell 115

Dipartimento di Fisica e Astronomia, Università di Bologna, via C. Ranzani 1, I-40127 Bologna, Italy
INAF - Istituto di Radioastronomia, via P. Gobetti 101, I-40129 Bologna, Italy
INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica, via E. Bassini 15, I-20133 Milano, Italy
Author to whom correspondence should be addressed.
Academic Editors: Stefano Ettori and Dominique Eckert
Received: 9 September 2016 / Revised: 12 November 2016 / Accepted: 15 November 2016 / Published: 23 November 2016
(This article belongs to the Special Issue Exploring the Outskirts of Galaxy Clusters)
View Full-Text   |   Download PDF [1184 KB, uploaded 24 November 2016]   |  


Giant radio relics are arc-shaped diffuse sources with Mpc-scale found in the peripheries of some dynamically disturbed galaxy clusters. According to the leading scenario of relic formation, shock waves occurring in merger events amplify the local magnetic field and (re)accelerate particles. However, Mach numbers associated with merger shocks are typically low, and hence inefficient at accelerating particles from the thermal pool. We analyzed a deep Chandra observation (334 ks) to study the relic region in the cluster Abell 115. Temperature and surface brightness profiles taken across the relic both show a clear discontinuity, which is consistent with a shock. This result supports the relic–shock connection and represents a test case to study the origin of radio relics. In this particular case, we suggest that a re-acceleration scenario is more suitable. The relic morphology and position are consistent with a shock produced in an off-axis merger between clusters with different masses. View Full-Text
Keywords: shock waves; radiation mechanisms; non-thermal processes; galaxy clusters shock waves; radiation mechanisms; non-thermal processes; galaxy clusters

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Botteon, A.; Gastaldello, F.; Brunetti, G.; Dallacasa, D. Relic—Shock Connection in Abell 115. Galaxies 2016, 4, 68.

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