An international team of scientists from Italy and the United States has found that the mysterious radio source in the galaxy cluster Abell 2626 is turbulent vortices in the intergalactic medium that accelerate charged particles. This is reported in a preprint published in the arXiv.org repository.
Abell 2626 is 700 million light years from Earth. It is an open galaxy cluster (cluster) with a radius of 1.6 megaparsec (one megaparsec equals 3.2 million light years). The brightest galaxy in the cluster is IC5338, which contains two nuclei. Another galaxy - IC5337 - resembles a jellyfish in shape, since part of the material is "blown away" from it due to movement in the relatively dense environment of the cluster.
One of the features of the Abell 2626 is several symmetrical arc structures visible in the radio frequency range, whose origin has long remained unknown. Some scientists believed that they were associated with a radio halo - a source of radio emission that is usually located in the centers of galactic clusters. An alternative explanation was that the arcs appeared as a result of the gravitational interaction of two IC5338 cores. However, only two arcs (north and south) were known at that time, and the discovery of two new arcs (west and east) cast doubt on such a model.
The researchers took advantage of new data from the Chandra X-ray telescope, which scientists hoped to find an active galactic nucleus associated with an additional pair of radio frequency arcs. They searched for hot and cold emissions of matter from nearby galaxies that could cause anomalous radio emission. Scientists have found that arcs can be a bright part of an unnoticeable radio halo that arose from the turbulent motion of gas and the associated acceleration of relativistic electrons.
However, astronomers also believe that a rare case is possible when anomalous radio emission is caused by a collision of a gas in an intergalactic medium with a plasma from an active galactic nucleus moving at a relativistic speed (close to the speed of light).
