A team of astronomers in South Africa has used the MeerKAT radio telescope to make the most detailed study of these radio structures yet, gaining new insight into some of the most massive events in the Universe.
“These structures are full of surprises and much more complex than what we initially thought,” says astronomer Francesco de Gasperin of the University of Hamburg in Germany and the National Institute for Astrophysics in Italy.
“The shock waves act as giant particle accelerators that accelerate electrons to speeds close to the speed of light. When these fast electrons cross a magnetic field, they emit the radio waves that we see.”
“The shocks are threaded by an intricate pattern of bright filaments that trace the location of giant magnetic field lines and the regions where electrons are accelerated.”
Galaxy clusters are the largest structures in the Universe that are held together by gravity. They can be gargantuan, comprising hundreds or thousands of separate galaxies. Galaxies and galaxy clusters travel along filaments of the cosmic web to cluster nodes, where they join to form even bigger clusters.
These massive events take place at high velocities. As a result, cluster-scale shock waves are generated that also traverse at high velocities through space.
This cluster, called Abell 3667, is still coming together. At least 550 galaxies have been associated with it, and the shock waves are traveling through it at velocities around 1,500 kilometers per second (930 miles per second).
The shocks that are associated with cluster mergers are called radio relics, and they can be used to find the properties of the intergalactic space within the cluster, known as the intracluster medium, and intracluster dynamics.
Abell 3667, at around 700 million light-years away, is relatively close to us, and quite massive. This means it can be analyzed for information.
MeerKAT is a precursor to and pathfinder for the Square Kilometre Array (SKA) that is currently being developed across Australia and South Africa to provide a unique radio eye on the sky.
MeerKAT’s observations and those of the Australian Square Kilometer Array Pathfinder are paving way for future endeavors in the arena.
“Our observations have unveiled the complexity of the interplay between the thermal and non-thermal components in the most active regions of a merging cluster,” the researchers write in their study.
“Both the intricate internal structure of radio relics and the direct detection of magnetic draping around the merging bullet are powerful examples of the non-trivial magnetic properties of the intracluster medium. Thanks to its sensitivity to polarized radiation, MeerKAT will be transformational in the study of these complex phenomena.”
The research has been published in Astronomy & Astrophysics.