An international team of scientists has found evidence for the first time that shock waves are passing through the “cosmic web”, a massive network of intertwining galactic filaments. This means that magnetic fields run along the largest structure in the Universe, consisting of gas, dust and dark matter that binds galaxies.
Image source: icrar.org
In the sixties of the last century, scientists began to lean towards the idea that when looking at the universe on the largest scales, there is some kind of order, reminiscent of a web with threads. They cross voids (large voids) and cause galaxies to form clusters. Two decades later, computer simulations were able to determine what such a universal network might look like.
Since then, astronomers have mapped the galactic web, based on actual observations, in an attempt to answer questions about its structure. And only one element did not yield to observation – the magnetic fields propagating throughout this cosmic structure. When matter in the universe merges, shock waves are created that accelerate particles and thereby strengthen intergalactic magnetic fields. The galactic filaments are pulled together by gravitational forces, and the resulting magnetic fields, which are stronger because of this, should generate radio waves that can be observed from Earth. Until now, such a “glow” of galactic filaments in the radio frequency range could not be fixed due to the weakness of the signals.
They were discovered by comparing data from the GMIMS (Global Magneto-Ionic Medium Survey), Planck Legacy Archive, Owens Valley Long Wavelength Array and Murchison Widefield Array projects for known clusters and galactic filaments. Success was achieved by an international team of scientists led by Dr. Tessa Vernstrom (Tessa Vernstrom) from the University of Western Australia. The researchers began looking for signals in 2020, but when they first recorded them, they could not distinguish them from the “background noise” created by galaxies and other objects. So they began looking for another type of signal—polarized radio emission, less susceptible to distortion caused by the noise of other objects. By identifying them, the scientists were able to provide compelling evidence for the observation of signals from shock waves in the largest structures of the universe and confirm that their models correspond to reality.
Comparing these data, the scientists aimed to amplify the radio waves and compared the resulting picture with modern cosmological simulations built on the basis of hydrodynamic astrophysical calculations of the Enzo project. As a result, it was possible to build the first model of a cosmological network that predicts polarized radio emission generated by shock waves of galactic filaments.
The discovery will help in expanding and refining modern theories about the mechanisms of the expansion of the Universe, as well as in unraveling the origin of cosmic magnetism.
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