Astronomers Spotted a Radio Relic in a Low-mass and Nearby Galaxy Cluster


An international team of astronomers utilizing the MeerKAT radio telescope in South Africa has spotted a radio relic in a low-mass and nearby merging galaxy cluster dubbed A2384. 

Galaxy cluster A2384 comprises two components, named A2384 (N) and A2384 (S), displaying a dense X-ray filament between them, measured to be almost 2.3 million light-years long. Here is what you need to know.

Newly Found Radio Relic Features and Other Significant Details

A team of astronomers supervised by Viral Parekh of the Rhodes University in Makhanda, South Africa, discovered A2384 with MeerKAT back in May 2019. They spotted an extended radio source situated at the edge of the galaxy cluster that turned out to be only a single radio relic. 

The recently discovered radio source is perpendicular to the A2384 merger axis, elongating from the south-east to the north-west. Its size is around 2.7 by 0.86 million light-years, and the radio power of the source at 1.4GHz was estimated to be 387 million PW/Hz. Astronomers observed that it is a radio relic associated with the A2384 cluster and the merger shock. 

The Source of the Radio Relic

Trying to explain the radio relic source, the team thinks it is most likely the result of shock wave propagation during the low-mass A2384 (S) cluster through the massive A2384 (N) cluster. Such a thing might create a trail, as a hot X-ray filament between the cluster’s two components. 

The MeerKAT data unveiled that the relic in A2384 is an extremely steep spectrum source, with the spectral index at around -2.5. According to the team, it means that the re-acceleration of the pre-relativistic electrons in the presence of the merger shock. 

“[…], sub-cluster A2384 (S) has passed through A2384(N) and is likely to have removed a large amount of hot gas from both systems in the direction of the merger,” detailed the astronomers.

Besides the recent finding, the team also spotted a candidate radio ridge in the cluster’s X-ray filament. That ridge is small, and the astronomers think it could represent a new type of radio source, between the two components of A2384.

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