LOFAR, VLA, and Chandra observations of the Toothbrush galaxy cluster
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dc.type
JournalArticle
pl
dc.abstract.en
We present deep LOFAR observations between 120 and 181 MHz of the “Toothbrush” (RX J0603.3+4214), a
cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and
novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the
spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new
information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We
derive a spectral index of \alpha = -0.8 \pm 0.1 at the northern edge of the main radio relic, steepening toward the south
to \alpha \approx -2. The spectral index of the radio halo is remarkably uniform (\alpha = -1.16, with an intrinsic scatter of
\leqslant 0.04). The observed radio relic spectral index gives a Mach number of M = 2.8\frac{+0,5}{-0,3}, assuming diffusive shock
acceleration. However, the gas density jump at the northern edge of the large radio relic implies a much weaker
shock (M \approx 1.2, with an upper limit of M \approx 1.5). The discrepancy between the Mach numbers calculated from
the radio and X-rays can be explained if either (i) the relic traces a complex shock surface along the line of sight, or
(ii) if the radio relic emission is produced by a re-accelerated population of fossil particles from a radio galaxy. Our
results highlight the need for additional theoretical work and numerical simulations of particle acceleration and reacceleration
at cluster merger shocks
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dc.subject.en
galaxies: clusters: individual: RX J0603.3+4214
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dc.subject.en
galaxies: clusters: intracluster medium
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dc.subject.en
large-scale structure of Universe
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dc.subject.en
radiation mechanisms: non-thermal
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dc.subject.en
X-rays: galaxies: clusters
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dc.description.volume
818
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dc.description.number
2
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dc.identifier.doi
10.3847/0004-637X/818/2/204
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dc.identifier.eissn
1538-4357
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dc.title.journal
The Astrophysical Journal
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dc.language.container
eng
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dc.affiliation
Wydział Fizyki, Astronomii i Informatyki Stosowanej : Instytut – Obserwatorium Astronomiczne
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dc.subtype
Article
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dc.identifier.articleid
204
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dc.rights.original
CC-BY; inne; ostateczna wersja wydawcy; po opublikowaniu; 12;
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.pointsMNiSW
[2016 A]: 40
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