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19th of February 2021
Radio Cosmic Web Filament Detection
by Vernstrom et al.
Filaments connecting clusters of galaxies are notoriously hard to detect due to their faint and diffuse nature. Only two short bridges have ever been imaged in the radio before. Vernstrom et al. recently stacked nearly 400,000 pairs of clusters to look for an average signal from these filaments. Maps from three frequencies from the GLEAM survey using the Murchison Widefield Array and one from the Owens Valley Radio Observatory Long Wavelength Array were used for the stacking. This resulted in the first average detection of diffuse radio emission between widely separated pairs of clusters, as is shown in the left image. This was compared with a stacked sample of cluster pairs with large separations in 3-dimeniosnal space, or large changes in redshift between them. This control sample should not show any detection, and this is what is seen in the centre image. The strength of the emission was compared with cosmological magnetohydrodynamic simulations, a cutout of one simulation is shown in the right panel with lines indicating possible pairs of clusters. The radio detections show a stronger signal than predicted by simulations, indicating either a stronger magnetic field strength or more efficient particle acceleration. More details are give in the preprint of the paper and an article on the Space Australia website.

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