The cosmic web winds around cosmic voids millions of light years across. Predicted by astrophysicists in the 1960s, computer models showed what this massive network really looked like in the 1980s.
Scientists have 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 major concerns.
How do magnetic fields behave on a cosmic scale? What role do they play in the formation of both galactic and cosmic structures? These questions remain a focus.
We are learning more about these cosmic magnetic fields from recent research conducted by the International Center for Radio Astronomy Research (ICRAR) in collaboration with the CSIRO, Australia’s national science agency.
Dr. Tessa Vernstrom, of the University of Western Australia (UWA) ICRAR node, is the lead author of the study and describes magnetism as a fundamental force in nature.
Dr Vernstrom 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 phenomenon had previously only been observed in the largest clusters of galaxies in the Universe and was predicted 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 really conclusively detected due to the weakness of the signals.”
Vernstrom chose polarized radio light as the signal type because it has less background noise. After all, in addition to the shock waves, the first transmissions may also contain emissions from galaxies and other astronomical objects.
Dr Vernstorm 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 the study, scientists used data and radio maps of the entire sky from the Global Magneto-Ionic Medium Survey, the Planck Legacy Archive, the Owens Valley Long Wavelength Array and the Murchison Widefield Array, stacking 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, Jennifer West, et al. Polarized accretion shocks of the cosmic web. Science Progress. DOI: 10.1126/sciadv.ade7233