Utilizing the LOw Frequency ARray (LOFAR), astronomers from the College of Bologna, Italy and elsewhere, have performed radio observations of the close by galaxy cluster Abell 2142. In end result, they detected a brand new element of the cluster’s large radio halo. The discovering was offered in a paper printed August 15 on the pre-print server arXiv.
Galaxy clusters comprise as much as 1000’s of galaxies sure collectively by gravity. They’re the most important identified gravitationally sure constructions within the universe, and will function glorious laboratories for learning galaxy evolution and cosmology.
Radio halos are huge areas of diffuse radio emission, often discovered on the facilities of galaxy clusters. Nevertheless, diffuse emissions typically have very low floor brightness, significantly at GHz frequencies, which makes them onerous to detect. Their brightness will increase at lower frequencies, unveiling the presence of those areas. The most effective devices to review radio haloes at low frequencies with unprecedented element and sensitivity is LOFAR—resulting from its functionality of acquiring deep, high-resolution, high-fidelity and low-frequency radio pictures.
Positioned some 1.24 million gentle years away, Abell 2142 (or A2142 for brief) is a close-by X-ray luminous galaxy cluster. It comprises at the least 900 galaxies (inside a radius of roughly 11.4 million gentle years) which might be hierarchically organized in lots of constructions and sub-structures sometimes consisting of small teams.
Earlier radio observations of Abell 2142 have discovered that it hosts a large radio halo with two elements, named H1 and H2, that are characterised by totally different morphological and spectral properties. H1, also called the “core” is the brighter, extra firm and roundish out of the 2. In terms of H2, or the “ridge,” it’s bigger than H1, fainter, and showcases an elongated form.
Not too long ago, a staff of astronomers led by College of Bologna’s Luca Bruno has determined to take a more in-depth have a look at the radio halo in Abell 2142 utilizing LOFAR. The examine, complemented by archival multi-frequency radio and X-ray information, offered extra insights into the construction of this halo.
LOFAR observations have unveiled the presence of the radio halo’s third element—H3. The outcomes point out that H3’s radio emission follows the X-ray thermal distribution of the intracluster medium (ICM) as much as scales better than 6.5 million gentle years.
H3 has dimensions of about 7.8 by 6.5 million gentle years, spectral index of 1.57, and showcases exponential floor brightness profile, in addition to sub-linear radio/X-ray spatial correlation. These findings allowed the staff to categorise H3 as a large ultra-steep spectrum radio halo.
Attempting to elucidate the origin of H3, the authors of the paper supply two hypotheses. They suppose that H3 could also be a results of an outdated energetic merger or inefficient turbulent re-acceleration induced by ongoing minor mergers.
“In each these two situations, H2 might have been the interior a part of H3, which has then been reshaped by turbulence into the current ridge,” the researchers concluded.
Extra data:
L. Bruno et al, A 3-component large radio halo: the puzzling case of the galaxy cluster Abell 2142, arXiv (2023). DOI: 10.48550/arxiv.2308.07603
Journal data:
arXiv
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European astronomers detect new element of radio halo in a close-by galaxy cluster (2023, August 23)
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