Cluster Mergers and the Origin of the ARCADE-2 Excess

Abstract

Radio observations at multiple frequencies have detected a significant isotropic emission component between 22~MHz and 10~GHz, commonly termed the ARCADE-2 Excess. The origin of this radio emission is unknown, as the intensity, spectrum and isotropy of the signal are difficult to model with either traditional astrophysical mechanisms or novel physics such as dark matter annihilation. We posit a new model capable of explaining the key components of the excess radio emission. Specifically, we show that the re-acceleration of non-thermal electrons via turbulence in merging galaxy clusters are capable of explaining the intensity, spectrum, and isotropy of the ARCADE-2 data. We examine the parameter spaces of cluster re-acceleration, magnetic field, and merger rate, finding that the radio excess can be reproduced assuming reasonable assumptions for each. Finally, we point out that future observations will definitively confirm or rule-out the contribution of cluster mergers to the isotropic radio background.

24 pages, 8 figures

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Cited by in corpus (15)

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• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• The Radio Background Below 100 MHz
• The Radio Synchrotron Background: Conference Summary and Report
• Analytical model for cluster radio relics
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• Contributions of dark matter annihilation to the global 21cm spectrum observed by the EDGES experiment
• Constraint on Primordial Magnetic Fields In the Light of ARCADE 2 and EDGES Observations
• A Stimulating Explanation of the Extragalactic Radio Background
• Exploring diffuse radio emission in galaxy clusters and groups with the uGMRT and the SKA
• Measurement of the Anisotropy Power Spectrum of the Radio Synchrotron Background
• Radio-relic and the diffuse emission trail discovered in a low mass galaxy cluster Abell 1697
• Diffuse Sources, Clustering and the Excess Anisotropy of the Radio Synchrotron Background
• High-energy neutrino constraints on cosmic-ray re-acceleration in radio halos of massive galaxy clusters
• Some Implications of the Leptonic Annihilation of Dark Matter: Possible Galactic Radio Emission Signatures and the Excess Radio Flux of Extragalactic Origin