A shock at the radio relic position in Abell 115

We analysed a deep Chandra observation (334 ks) of the galaxy cluster Abell 115 and detected a shock cospatial with the radio relic. The X-ray surface brightness profile across the shock region presents a discontinuity, corresponding to a density compression factor C=2.0± 0.1, leading to a Mach number M=1.7± 0.1 (M=1.4-2 including systematics). Temperatures measured in the upstream and downstream regions are consistent with what expected for such a shock: T_u=4.3^+1.0_-0.6 keV and T_d=7.9^+1.4_-1.1 keV, respectively, implying a Mach number M=1.8^+0.5_-0.4. So far, only few other shocks discovered in galaxy clusters are consistently detected from both density and temperature jumps. The spatial coincidence between this discontinuity and the radio relic edge strongly supports the view that shocks play a crucial role in powering these synchrotron sources. We suggest that the relic is originated by shock re-acceleration of relativistic electrons rather than acceleration from the thermal pool. The position and curvature of the shock and the associated relic are consistent with an off-axis merger with unequal mass ratio where the shock is expected to bend around the core of the less massive cluster.

Volume

460

Issue

1

Start page

L84

Uri

http://hdl.handle.net/20.500.12386/24766

Url

https://academic.oup.com/mnrasl/article/460/1/L84/2589744

Issn Identifier

0035-8711

Ads BibCode

2016MNRAS.460L..84B

Rights

open.access

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Name

1604.07823.pdf

Description

postprint

Size

493 KB

Format

Adobe PDF

Checksum (MD5)

52afa0033e825f9fcaefcaa18e516222

Name

Mon. Not. R. Astron. Soc Lett. 2016 Botteon.pdf

Description

PDF editoriale

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1.99 MB

Format

Adobe PDF

Checksum (MD5)

966ad7cfa86ebb7b56c2adbe7eb742e4

A shock at the radio relic position in Abell 115

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