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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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