MeerKAT's View of the Bullet Cluster 1E 0657-55.8
Date Issued
2023
Author(s)
Abstract
The Bullet cluster (1E 0657-55.8) is a massive merging system at redshift
$z$=0.296, known to host a powerful radio halo and a relic. Here we present
high fidelity MeerKAT L-band (0.9-1.7 GHz) observations of the Bullet cluster,
in which we trace a larger extent of both the radio halo and relic in
comparison to previous studies. The size of the recovered radio halo is 1.6 Mpc
$\times$ 1.3 Mpc and the largest linear size of the relic is ~988 kpc. We
detect a new decrement feature on the southern outskirts of the halo emission,
where a region appears to have a lower surface brightness in comparison to its
surroundings. The larger extension on the outskirts of the halo is faint, which
suggests lower relativistic electron density or a weaker magnetic field. An
in-band spectral index map of the radio halo reveals a hint of radial
steepening towards the edges of the diffuse source, likely due to synchrotron
electron ageing. The integrated spectral index of the radio halo is
1.1$\pm$0.2. We perform a radio-X-ray surface brightness point-to-point
analysis, which reveals a linear correlation for the radio halo. This indicates
that the radio halo emission is produced by primary re-acceleration mechanisms.
Finally, we derive a radio Mach number of M_R= 4.6$\pm$0.9 for the relic shock
region, which is higher than the Mach number inferred by earlier analyses based
on X-ray data. Discrepancies between radio and X-ray Mach numbers have been
observed for multiple systems, with studies suggesting that this is due to
various factors, including relic orientation.
Volume
518
Issue
3
Start page
4595
Issn Identifier
0035-8711
Rights
open.access
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