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Galaxy clusters contain hundreds, or even thousands, of individual
galaxies. However, these galaxies represent only a few percent of a
cluster's total mass. About 80% of it is dark matter, and the rest is
a hot plasma: gas heated to above 10,000,000 degrees and interwoven
with weak magnetic fields. An international team led by Chris Riseley
have identified a series of rarely observed radio objects -- a radio
relic, a radio halo and fossil radio emission -- within a particularly
dynamic galaxy cluster called Abell 3266.
The team used new data from the ASKAP radio telescope and the
Australia Telescope Compact Array (ATCA) to study Abell 3266 in
detail. "Radio relics" are arc-shaped features that sit towards a
cluster's outskirts, powered by shockwaves travelling through the
plasma, which cause a jump in density or pressure, and energise the
particles. An example of a shockwave on Earth is the sonic boom that
happens when an aircraft breaks the sound barrier.
The concave shape of the relic pictured above is unusual, earning it the moniker of a “wrong-way” relic.
Overall, the new data break our understanding of how relics are generated, and the team are
still working to decipher the complex physics behind these radio objects.
More information is given in
this article in The Conversation.
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