Tomasz Nowakowski is a member of the physics.org community.
Astronomers using various radio telescopes have been observing a merging galaxy cluster. The campaign gave more insight into the radio halo. There was a paper published on arXiv.org.
A radio halo is a large area of radio emission. diffuse emissions have low surface brightness and are hard to detect. The presence of these regions is revealed by their brightness increasing at lower frequencies.
LOw Frequency Array is an excellent tool for studying radio halos with unprecedented detail and sensitivity. A group of researchers led by Kamlesh Rajpurohit of the University of Bologna in Italy used LOFAR in order to inspect the radio halo in Abell 2256, a nearby massive galaxy cluster. The team used the upgraded Giant Metrewave Radio Telescope to observe the halo.
The first detailed analysis of the radio halo in the merging galaxy cluster Abell 2256 was presented by us. The researchers wrote in the paper that they were able to study the halo emission with unprecedented detail.
The radio images of Abell 2256 were the first of their kind. They were able to detect the halo emission at all frequencies. The largest linear size of the halo was measured to be about 2.97 million light years at 1.5 GHz and about 2.97 million light years at 144 MHz.
The study found that emission from the halo follows a power-law spectrum between 150 MHz and 1.5 GHz and has an ultra steep spectrum with an integratedspectral index of 1.63. The maps showed a steepening with increasing radius.
The radio halo is similar to the X-rays in its structure. There is an X-ray peak in the main mass component. There is a correlation between the radio and X-ray surface brightness.
There was an anti-correlation between the X-ray surface brightness and the wavelength. This is consistent with steepening.
The authors of the paper said that the properties of radio halo make it a very peculiar object and that further investigation may advance our knowledge about particle acceleration mechanisms on very large scales.
More information: K. Rajpurohit et al, Deep low-frequency radio observations of Abell 2256 II: The ultra-steep spectrum radio halo. arXiv:2209.03288v1 [astro-ph.CO], arxiv.org/abs/2209.03288There is a science network.
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