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Galaxy clusters are huge structures found at the intersections of the
cosmic web. A single cluster can span millions of light-years across
and be made up of hundreds, or even thousands, of 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
"soup": 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. While the cluster has all the
hallmarks of a system that should be host to relics and haloes -- none
had been detected until recently.
The team used new data from the ASKAP radio telescope and the
Australia Telescope Compact Array (ATCA) to study Abell 3266 in more
detail. Galaxy clusters allow us to study a broad range of rich
processes -- including magnetism and plasma physics -- in environments
we can’t recreate in our labs. When clusters collide with each other,
huge amounts of energy are put into the particles of the hot plasma,
generating radio emission. And this emission comes in a variety of
shapes and sizes.
The data paint a complex picture, as shown in the image above: yellow
colours (ATCA data) show features where energy input is active. The blue haze
represents the hot plasma, captured at X-ray wavelengths by XMM-Newton. Redder
colours show features that are only visible at lower frequencies (ASKAP data). This
means these objects are older and have less energy. Either they have
lost a lot of energy over time, or they never had much to begin with.
More information is given in
this article in The Conversation.
(Image credit: Christopher Riseley, Università di Bologna)
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