LOFAR detection of extended emission around a mini-halo in the galaxy cluster Abell 1413
arXiv (Cornell University)(2023)
摘要
The relation between giant radio halos and mini-halos in galaxy clusters is
not understood. The former are usually associated with merging clusters, the
latter are found in relaxed systems. In the last years, the advent of
low-frequency radio observations has challenged this dichotomy, finding
intermediate objects with a hybrid radio morphology. We aim to investigate the
presence of diffuse radio emission in the cluster Abell 1413 and determine its
dynamical status. We used LOFAR HBA observations centred at 144 MHz to study
the diffuse emission hosted by this cluster.To investigate the dynamical state
of the system, we complete our study with newly analysed XMM-Newton archival
data. A1413 shows features that are typically present in both relaxed (e.g.,
peaked x-ray surface brightness distribution and little large-scale
inhomogeneities) and disturbed (e.g., flatter temperature and metallicity
profiles) clusters.This evidence supports the scenario that A1413 is neither a
disturbed nor fully relaxed object. We argue that it is an intermediate-phase
cluster.Using radio observations at 144 MHz, we discover the presence of a
wider diffuse component surrounding the previously reported mini-halo at the
cluster centre. By fitting the radio surface brightness profile with a
double-exponential model, we can disentangle the two components. We find an
inner mini-halo with an e-folding radius r_e1=28 kpc and the extended component
with r_e2 = 290 kpc. We also performed point-to-point correlations between
radio and X-ray surface brightness, finding a sub-linear relation for the outer
emission and a super-linear relation for the mini-halo.The mini-halo and the
diffuse emission extend over different scales and show different features,
confirming the double nature of the radio emission and suggesting that the
mechanisms responsible for the re-acceleration of the radio-emitting particle
might be different.
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关键词
extended emission,galaxy
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