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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 only been done 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. In this work, we performed 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 ($r_s 0.7$) 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 that 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 fitted a model to the radio emission in the context of turbulent re-acceleration with a constant ratio between thermal and non-thermal particles' energy densities and a magnetic field profile linked to the thermal gas density as $B(r) th $. We found that this simple model cannot reproduce the behaviour of the observed radio emission.
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 only been done 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. In this work, we performed 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 ($r_s 0.7$) 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 that 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 fitted a model to the radio emission in the context of turbulent re-acceleration with a constant ratio between thermal and non-thermal particles' energy densities and a magnetic field profile linked to the thermal gas density as $B(r) th $. We found that this simple model cannot reproduce the behaviour of the observed radio emission.
Clusters of galaxies are known to be turbulent environments, whether they are merging systems where turbulence is injected via the conversion of gravitational potential energy into the intracluster medium (ICM), or whether they are relaxed systems in which small-scale core sloshing is occurring within the potential well. In many such systems, diffuse radio sources associated with the ICM are found: radio haloes and mini-haloes. Abell 2142 is a rich cluster undergoing an extreme episode of core sloshing, which has given rise to four cold fronts and a complex multi-component radio halo. Recent work revealed that there are three primary components to the halo that spans a distance of up to around 2.4\,Mpc. The underlying physics of particle acceleration on these scales is poorly explored, and requires high-quality multi-frequency data with which to perform precision spectral investigation. We aim to perform such an investigation. We used new deep MeerKAT L-band (1283\,MHz) observations in conjunction with LOFAR HBA (143\,MHz) data as well as X-ray data from XMM-Newton and Chandra to study the spectrum of the halo and the connection between the thermal and non-thermal components of the ICM. We confirm the presence of the third halo component, detecting it for the first time at 1283\,MHz and confirming its ultra-steep spectrum nature, as we recovered an integrated spectrum of $ H3, \, total 0.10$. All halo components follow power-law spectra with increasingly steep spectra moving towards the cluster outskirts. We profiled the halo in three directions, finding evidence of asymmetry and spectral steepening along an axis perpendicular to the main axis of the cluster. Our investigation of the thermal non-thermal connection shows sub-linear correlations that are steeper at 1283\,MHz than 143\,MHz, and we find evidence of different connections in different components of the halo. In particular, we find both a moderate anti-correlation (H1, the core) and positive correlation (H2, the ridge) between the radio spectral index and X-ray temperature. Our results are broadly consistent with an interpretation of turbulent (re-)acceleration following an historic minor cluster merger scenario in which we must invoke some inhomogeneities. However, the anti-correlation between the radio spectral index and X-ray temperature in the cluster core is more challenging to explain; the presence of three cold fronts and a generally lower temperature may provide the foundations of an explanation, but detailed modelling is required to study this further.
We present a comprehensive multi-wavelength study of Supernova Remnant SN386 (G7.7-3.7), integrating existing observations from radio, X-ray, and optical wavelengths. Radio observations from MOST and VLA reveal a nearly circular shell with extended bright regions in the west and south borders, while MeerKAT observations reveal thin filaments with faint blowouts along the perimeter. The blowouts suggest the localized magnetic field weakening at the boundaries of G7.7-3.7 and non-uniform mass outflow from the progenitor star. The radio emission analysis indicates a flat spectrum, \(\alpha\) \(\simeq\) -0.32, with a steep spectral index, $\alpha$ $\simeq$-0.6, at the west border. MeerKAT polarization studies reveal magnetic field orientation aligned along the filaments rather than the overall shell structure as in MOST. X-ray morphology unveils a non-uniform distribution of X-ray emissions with bright arc-like features corresponding to southern radio emissions. The X-ray spectroscopic analysis shows that the arc-like feature is characterized by under-ionized plasma with low ionization timescale, 2.4 \(^{+1.1}_{-1.3}\) \(\times\) 10 \(^{10}\) cm \(^{-3}\) s, inferring a shocked age of 1.2 ± 0.6 kyr consistent with the supernova of 386 CE. Optical observations reveal filamentary structures aligned in the east-west direction with X-ray emission in H$\alpha$ + [NII], [OIII] and [SII] narrow-band filters. Optical long slit spectroscopy of one filament reveals [SII]/H$\alpha$ = (1.6-2.5) expected for shock-heated SNR and [NII]/H$\alpha$ greater than 2 indicating a gas enriched in nitrogen, suggesting collision with circumstellar material forming optical filaments. The study suggests a multi-faceted nature of G7.7-3.7, with localized weakening of magnetic field on the edges of non-uniform mass outflow, expanding in non-uniform density ISM and interacting with ISM mixed with circumstellar material.
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