A study of halo and relic radio emission in merging clusters using the Murchison Widefield Array

Abstract

We have studied radio haloes and relics in nine merging galaxy clusters using the Murchison Widefield Array (MWA). The images used for this study were obtained from the GaLactic and Extragalactic All-sky MWA (GLEAM) Survey which was carried out at 5 frequencies, viz. 88, 118, 154, 188 and 215 MHz. We detect diffuse radio emission in 8 of these clusters. We have estimated the spectra of haloes and relics in these clusters over the frequency range 80-1400 MHz; the first such attempt to estimate their spectra at low frequencies. The spectra follow a power law with a mean value of $\alpha =-1.13\pm 0.21$ for haloes and $\alpha =-1.2\pm 0.19$ for relics where, $S\propto {\nu }^{\alpha }$. We reclassify two of the cluster sources as radio galaxies. The low frequency spectra are thus an independent means of confirming the nature of cluster sources. Five of the nine clusters host radio haloes. For the remaining four clusters, we place upper limits on the radio powers of possible haloes in them. These upper limits are a factor of 2-20 below those expected from the $L_{\mathrm{X}}-P_{1.4}$ relation. These limits are the lowest ever obtained and the implications of these limits to the hadronic model of halo emission are discussed.

15 pages, 4 figures, accepted to MNRAS

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• Exploring the spectral properties of radio relics I: Integrated spectral index and Mach number
• The intra-cluster magnetic field in the double relic galaxy cluster Abell 2345
• Particle re-acceleration and Faraday-complex structures in the RXC J1314.4-2515 galaxy cluster
• The correlation between radio power and Mach number for radio relics in galaxy clusters
• Role of intracluster supernovae in radio mini-halos in galaxy clusters
• A Semi-Analytical Model for the Formation and Evolution of Radio Relics in Galaxy Clusters
• Radio Halo Detection in MWA Data using Deep Neural Networks and Generative Data Augmentation