Astronomers Spot Faint Glow of Shock Waves Along Cosmic Web
Astronomers have for the first time ever spotted the faint glow of shock waves rippling along strands of the cosmic web, an immense network of filaments and nodes that links the universe. This discovery, reported in the journal Science Advances, not only confirms the predictions of cosmic web simulations, but it also offers a rare peek at the magnetic fields that permeate the cosmic web, if only indirectly.
The discovery was made by a team led by Tessa Vernstrom, a senior research fellow at the International Centre for Radio Astronomy Research, University of Western Australia. To search for the faint signals, the researchers used data from several projects and observatories, including the Global Magneto-Ionic Medium Survey, the Planck Legacy Archive, the Owens Valley Long Wavelength Array and the Murchison Widefield Array to stack radio imaging from 612,025 galaxy cluster pairs, grouped together if they were close enough to be directly connected by cosmic web tendrils. The faint radio emissions from the shock waves were amplified by this stacking, surpassing the noisy background effects.
Dr. Tessa Vernstrom, the lead author of the study, mentioned that because only a few sources emit polarized radio light, the search was not as likely to be contaminated. This allowed them to provide stronger proof that the emissions come from shockwaves in the biggest structures in the universe, which corroborates the models for the development of this large-scale structure.
Charged particles are accelerated in the magnetic fields that make up the cosmic web by the shock waves present in filaments. As the particles move, light is emitted at wavelengths that are detected by radio telescopes. According to Dr Vernstrom, these new observations will help astronomers understand how magnetism works at the largest scales in the Universe. The discovery of these shock waves can allow astronomers to confirm the existence of the shock waves which was so far just a prediction by simulations.
These shock waves help to showcase large-scale magnetic fields that form something like a sheath around these filaments, said astrophysicist Marcus Brüggen of the University of Hamburg in Germany, who was not involved in the new study. Brüggen states that these shocks demonstrate the existence of immense magnetic fields that encase the filaments, resembling a sheath.
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