VLSS J0318.9+5755 (the Treble Clef) is a radio phoenix with ultra-steep spectrum in a massive merging cluster at z≈0.117 in the Zone of Avoidance, shaped by ICM gas motions that may also power a candidate radio halo.
CHEX-MATE: A LOFAR pilot X-ray$-$radio study on five radio halo clusters
2 Pith papers cite this work, alongside 1 external citations. Polarity classification is still indexing.
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abstract
The connection between the thermal and non-thermal properties in galaxy clusters hosting radio halos seems fairly well established. However, a comprehensive analysis of such a connection has been made only for integrated quantities (e.g. $L_X - P_{radio}$ relation). In recent years new-generation radio telescopes have enabled the unprecedented possibility to study the non-thermal properties of galaxy clusters on a spatially resolved basis. Here, we perform a pilot study to investigate the mentioned properties on five targets, by combining X-ray data from the CHEX-MATE project with the second data release from the LOFAR Two meter Sky survey. We find a strong correlation ($r_s \sim 0.7$) with a slope less than unity between the radio and X-ray surface brightness. We also report differences in the spatially resolved properties of the radio emission in clusters which show different levels of dynamical disturbance. In particular, less perturbed clusters (according to X-ray parameters) show peaked radio profiles in the centre, with a flattening in the outer regions, while the three dynamically disturbed clusters have steeper profiles in the outer regions. We fit a model to the radio emission in the context of turbulent re-acceleration with a constant ratio between thermal and non-thermal particles energy density and a magnetic field profile linked to the thermal gas density as $B(r) \propto n_{th}^{0.5}$. We found that this simple model cannot reproduce the behaviour of the observed radio emission.
years
2026 2representative citing papers
MACSJ0417’s giant radio halo shows spectral steepening and radio–X-ray correlation consistent with turbulence from a 6:1 off-axis merger that preserved the cool core; pure hadronic models are energetically excluded.
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The Treble Clef radio phoenix and its old nonthermal filaments
VLSS J0318.9+5755 (the Treble Clef) is a radio phoenix with ultra-steep spectrum in a massive merging cluster at z≈0.117 in the Zone of Avoidance, shaped by ICM gas motions that may also power a candidate radio halo.
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Multi-Wavelength Signatures of a Giant Cometary Radio Halo in MACSJ0417-1154
MACSJ0417’s giant radio halo shows spectral steepening and radio–X-ray correlation consistent with turbulence from a 6:1 off-axis merger that preserved the cool core; pure hadronic models are energetically excluded.