The cosmic web is the term used to refer to the clusters, filaments, and cavities that make up the large-scale structure of the universe. In the cosmology of Λ cold dark matter (ΛCDM), this web is formed by the anisotropic gravitational collapse of matter through primordial densities.
We’ve been able to map the cosmic web through observation for the past few decades, opening up the possibility of finding answers to some of astronomy’s most pressing problems. An area of particular interest is how magnetic fields behave on a cosmic scale and their role in the formation of galactic and cosmic structures.
ICRAR scientists discover tantalizing evidence of magnetic fields in the major cosmic structures of the universe.
Dr. Tessa Vernstrom from the University of Western Australia (UWA) ICRAR node said: “Magnetic fields permeate the universe – from planets and stars to the largest spaces between galaxies. However, many aspects of cosmic magnetism are not yet fully understood, especially on the scale seen in the cosmic web.”
“When matter merges into the universe, it produces a shock wave that accelerates particles and amplifies these intergalactic magnetic fields.”
The study recorded radio emissions from the cosmic web — the first observational evidence of strong shock waves. This event, previously seen only in the largest clusters of galaxies in the cosmos, was thought to be the “signature” of matter collisions throughout the cosmic web.
Dr Vernstrom said: “These shock waves give off radio emissions that should result in the cosmic web ‘glowing’ in the radio spectrum, but it was never conclusively detected due to the weak signals.”
In 2020, the team of Dr. Vernstrom searched for the “radio glow” of the cosmic web and discovered signals that may have originated from these cosmic waves. Vernstrom chose polarized radio light as the signal type because it has less background noise, as the first transmissions may contain emissions from galaxies and other astronomical objects in addition to the shock waves.
However, Vernstrom chose a different signal type with less background noise – polarized radio light – because these first signals may contain emissions from galaxies and astronomical objects other than the shock waves.
Vernstrom said, “Because very few sources emit polarized radio light, our search was less prone to contamination and we were able to provide much stronger evidence that we see emissions from the shock waves in the largest structures in the universe, helping to confirm our models.” for the growth of this large-scale structure.”
For this study, scientists used data and all-sky radio maps from the Global Magneto-Ionic Medium Survey, the Planck Legacy Archive, the Owens Valley Long Wavelength Array and the Murchison Widefield Array. The team stacked the data on the known clusters and filaments in the cosmic web.
The stacking method helps amplify the faint signal above the image noise, which was then compared to advanced cosmological simulations generated by the Enzo project.
These simulations are the first to include predictions of the polarized radio light from the cosmic shock waves observed as part of this study.
- Tessa Vernström et al. Polarized accretion shocks of the cosmic web. Scientific progress. DOI: 10.1126/sciadv.ade7233