A 3.5 Mpc-long radio relic in the galaxy cluster ClG 0217+70

Abstract

Mega-parsec scale radio sources in the form of halos and relics are often detected in dynamically disturbed galaxy clusters. Although they are associated with merger-induced turbulence and shocks, respectively, their formation is not fully understood. We aim to identify the mechanisms responsible for particle acceleration and magnetic field amplification in the halo and relics of the galaxy cluster ClG 0217+70. We observed ClG 0217+70 with LOFAR at 141 MHz and VLA at 1.5 GHz, and combine these observations with VLA 1.4 GHz archival data to study the morphological and spectral properties of the diffuse sources. We add Chandra archival data to examine the thermal and non-thermal properties of the halo. Our LOFAR and VLA 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 correlated, implying a tight relation between the thermal and non-thermal components. The diffuse radio structure in the south east with a projected size of 3.5 Mpc is the most extended radio relic detected to date. The spectral index across the relic width steepens towards the cluster centre, suggesting the electron ageing in the post-shock regions. The shock Mach numbers for the relics derived from the spectral index map 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 longer 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 plasma that could originate in active galactic nuclei.

References in corpus (22)

• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• Shocks and cold fronts in galaxy clusters
• The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release
• Compressible Turbulence in Galaxy Clusters: Physics and Stochastic Particle Re-acceleration
• The LOFAR Two Meter Sky Survey: Deep Fields, I -- Direction-dependent calibration and imaging
• Temperature profiles of a representative sample of nearby X-ray galaxy clusters
• Calibration of the galaxy cluster M_500-Y_X relation with XMM-Newton
• Radio signature of cosmological structure formation shocks
• The Case for Electron Re-Acceleration at Galaxy Cluster Shocks
• Statistics of Giant Radio Halos from Electron Reacceleration Models
• LOFAR observations of galaxy clusters in HETDEX
• Turbulence and Particle Acceleration in Giant Radio Haloes: the Origin of Seed Electrons
• Deep VLA observations of the cluster 1RXS J0603.3+4214 in the frequency range 1-2 GHz
• Deep radio observations of the radio halo of the bullet cluster 1E 0657-55.8
• Low-Frequency study of two clusters of galaxies: A2744 and A2219
• Second order Fermi reacceleration mechanisms and large scale synchrotron radio emission in intra-cluster bridges
• Deep LOFAR observations of the merging galaxy cluster CIZA J2242.8+5301
• VLA Radio Observations of the HST Frontier Fields Cluster Abell 2744: The Discovery of New Radio Relics
• Dissecting nonthermal emission in the complex multiple-merger galaxy cluster Abell 2744: Radio and X-ray analysis
• Morphology of radio relics I: What causes the substructure of synchrotron emission?
• Radio relics in PSZ2 G096.88+24.18: A connection with pre-existing plasma

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• The diffuse radio emission in the high-redshift cluster PSZ2 G091.83+26.11: total intensity and polarisation analysis with Very Large Array 1-4 GHz observations
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• A Semi-Analytical Model for the Formation and Evolution of Radio Relics in Galaxy Clusters
• Effects of large-scale magnetic fields on the observed composition of ultra high-energy cosmic rays
• The Coma cluster at LOFAR frequencies II: the halo, relic, and a new accretion relic
• Discovery of large-scale radio emission enveloping the mini-halo in the most X-ray luminous galaxy cluster RX~J1347.5-1145
• uGMRT and MeerKAT observation of RXCJ0232-4420: a quiet cluster with a giant radio halo
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