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تسجيل مستخدم جديدA 3.5 Mpc-long radio relic in the galaxy cluster ClG 0217+70
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Mega-parsec scale radio sources in the form of halos and relics are often detected in dynamically disturbed galaxy clusters and are generally thought to be generated by merger-induced turbulence and shocks, respectively. We aim to identify the mechanisms responsible for the particle acceleration and the magnetic field amplification in diffuse radio sources of the galaxy cluster ClG 0217+70. We observed the cluster with LOFAR at 141 MHz and VLA at 1.5 GHz, and combine with VLA 1.4 GHz archival data to study the morphological, spectral properties of the sources in the cluster. We add Chandra archival data to examine the thermal and non-thermal relation of the gas in the cluster centre. Our LOFAR and VLA new data confirm the presence of a giant radio halo in the cluster centre and multiple relics in the outskirts. The radio and X-ray emission from the halo are positively correlated, implying a tight relation between the thermal and non-thermal components. The SE radio structure with a projected size of 3.5 Mpc is the most extended radio relic detected to date. The spectral index across the width of the relics steepens towards the cluster centre, suggesting the energy ageing in the post-shock regions. The shock Mach numbers for the relics derived from the spectral index map reasonably range between 2.0 and 3.2. However, the integrated spectral indices lead to increasingly high Mach numbers for the relics farther from the cluster centre. This discrepancy could be because the relation between injection and integrated spectra does not hold for distant shocks, suggesting that the cooling time for the radio-emitting electrons is shorter than the crossing time of the shocks. The variations in the surface brightness of the relics and the low Mach numbers imply that the radio-emitting electrons are re-accelerated from fossil gas that is originally energised by active galactic nucleus activities.
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