Another shock for the Bullet cluster, and the source of seed electrons for radio relics

Timothy W Shimwell; Maxim Markevitch; Shea Brown; Luigina Feretti; B. M Gaensler; M Johnston-Hollitt; Craig Lage; Raghav Srinivasan

doi:10.1093/mnras/stv334

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Another shock for the Bullet cluster, and the source of seed electrons for radio relics

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Another shock for the Bullet cluster, and the source of seed electrons for radio relics

Timothy W Shimwell, Maxim Markevitch, Shea Brown, Luigina Feretti, B. M Gaensler, M Johnston-Hollitt, Craig Lage and Raghav Srinivasan

Monthly notices of the Royal Astronomical Society, Vol.449(2), pp.1486-1494

05/11/2015

DOI: 10.1093/mnras/stv334

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Abstract

With Australia Telescope Compact Array observations, we detect a highly elongated Mpc-scale diffuse radio source on the eastern periphery of the Bullet cluster 1E 0657−55.8, which we argue has the positional, spectral and polarimetric characteristics of a radio relic. This powerful relic (2.3 ± 0.1 × 1025 W Hz−1) consists of a bright northern bulb and a faint linear tail. The bulb emits 94 per cent of the observed radio flux and has the highest surface brightness of any known relic. Exactly coincident with the linear tail, we find a sharp X-ray surface brightness edge in the deep Chandra image of the cluster – a signature of a shock front in the hot intracluster medium (ICM), located on the opposite side of the cluster to the famous bow shock. This new example of an X-ray shock coincident with a relic further supports the hypothesis that shocks in the outer regions of clusters can form relics via diffusive shock (re-)acceleration. Intriguingly, our new relic suggests that seed electrons for reacceleration are coming from a local remnant of a radio galaxy, which we are lucky to catch before its complete disruption. If this scenario, in which a relic forms when a shock crosses a well-defined region of the ICM polluted with aged relativistic plasma – as opposed to the usual assumption that seeds are uniformly mixed in the ICM – is also the case for other relics, this may explain a number of peculiar properties of peripheral relics.

radiation mechanisms: non-thermal

radio continuum general

galaxies: clusters: individual: 1E 0657-55.8

galaxies: clusters: intracluster medium

acceleration of particles

shock waves

Details

Title: Subtitle: Another shock for the Bullet cluster, and the source of seed electrons for radio relics
Creators: Timothy W Shimwell - Leiden University
Maxim Markevitch - Goddard Space Flight Center
Shea Brown - University of Iowa
Luigina Feretti - Australia Telescope National Facility
B. M Gaensler - The University of Sydney
M Johnston-Hollitt - Australia Telescope National Facility
Craig Lage - Australia Telescope National Facility
Raghav Srinivasan - Victoria University of Wellington
Resource Type: Journal article
Publication Details: Monthly notices of the Royal Astronomical Society, Vol.449(2), pp.1486-1494
DOI: 10.1093/mnras/stv334
ISSN: 0035-8711
eISSN: 1365-2966
Publisher: Oxford University Press
Language: English
Date published: 05/11/2015
Academic Unit: Physics and Astronomy
Record Identifier: 9984199856902771

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