A giant, swirling section of the cosmic web is the largest individual swirling structure ever observed by astronomers.
A giant filament of the cosmic web is shown in the center of this illustration. The right part of the picture shows the rotation of neutral hydrogen in some galaxies, where red shows motion away from us, and blue shows motion toward us.
Credit: Lyla Jung
- Astronomers have identified the largest known single spinning structure within the cosmic web, a filament approximately 117,000 light years wide and 5.5 million light years long, located 424 million light years away.
- Observations from MeerKAT, DESI and SDSS revealed that 14 embedded galaxies display synchronized rotation, their individual spin directions aligned with the twist of the filament, indicating transfer of angular momentum from the large-scale structure to the galaxies.
- This discovery provides important insights into galaxy formation and the acquisition of angular momentum, especially given the high content of neutral hydrogen in these galaxies, which acts as a tracer for gas and momentum fluxes.
- Understanding these structures is essential to refine weak lensing observations, as their intrinsic galaxy alignment can otherwise contaminate data used to study dark matter and cosmic expansion and to leverage filaments as important cosmological probes.
About 424 million light-years away, a vast part of the cosmic web (the network-like distribution of matter displayed on the largest scale by the universe) appears as if it is caught in a vortex. It is the largest single rotating structure ever observed by astronomers, measuring approximately 117,000 light-years across and 5.5 million light-years long. The discovery also provides clues as to how early galaxies formed.
Scientists found it in survey data from South Africa’s MeerKAT radio telescope. Additional observations from the Dark Energy Spectroscopic Instrument (DESI) and Sloan Digital Sky Survey (SDSS) revealed more details.
First, they found a series of 14 galaxies with members moving toward us at one end and some moving away from us at the other end. This suggests that they are all moving together, moving at a leisurely (astronomically speaking) speed of 250,000 miles per hour.
Puzzled by this strange synchronicity, astronomers took a closer look and found that the cosmic web in which the galaxies are embedded is also rotating with them.
similar, but different
This has been happening before also. In the cosmic web the gas swirls here and there in eddies, flowing with unevenly distributed matter, like water hitting a rock in a stream. But every galaxy is also spinning, and most of them are spinning in the same direction as the filament; It is very strange that astronomers generally think that the direction of rotation of galaxies is random. At least in this case, it looks like the two may be linked, which could help us figure out how galaxies get their angular momentum in the first place.
“We believe in [alignment] This is caused by the gravitational interaction between the galaxies and the filaments,” said Madalina Tudorche, a postdoctoral research assistant at the University of Oxford, who led the study. “More specifically, such a massive transfer of angular momentum to galaxies. This is very important as we are trying to get a better picture of the formation and evolution of galaxies in the context of their environments.
Galaxies in this composition are filled with neutral hydrogen, the raw material for star formation. Because hydrogen is so easily disturbed, it acts like a motion detector, showing how gas and motion flow through the cosmic web. This makes this filament a kind of live demo of how galaxies gather and swirl the material needed for their growth.
we are looking for more
Finding more such structures could add additional pieces to the puzzle of galaxy evolution. “Statistically, we believe there are other rotating structures, some of which may be larger – however, we have not been able to detect them directly with our current data and telescopes,” Tudorche said. “With new data coming from radio telescopes (from MeerKAT to nuclear neutral hydrogen) and optical telescopes like Vera Rubin and Euclid, we plan to look at more of these structures to hopefully be able to describe them more accurately as a population.”
Scientists hope to understand them as much as possible because they can contaminate weak lensing observations, which enables astronomers to study the distribution of dark matter and the accelerating expansion of the universe. These observations are possible because the path of light bends as it travels vast distances through distorted space-time around matter.
Weak lensing results in a slight funhouse mirror effect that makes the background galaxies appear aligned. So if galaxies are aligned for a different reason (such as being coordinated with their filament), it may be mistaken for a weak lensing signal, making the data less accurate.
“Alignments between galaxies within filaments (or other cosmic structures) break our assumption that without gravitational lensing all galaxies are randomly oriented,” said Naomi Robertson, a postdoctoral research associate at the University of Edinburgh who was not involved in the study. “So we have to take this effect into account when we predict what our lensing measurements should look like. What’s interesting in this work now is that they’re finding greater alignment than the simulations predict.”
It is important to study these
Robertson says working with such observations gives astronomers a chance to test how they analyze this data so they can be better prepared to handle the Rubin and Euclid data. “Alignments inside filaments are not just a contaminant to weak lensing observations, filaments are actually interesting cosmological probes in their own right,” she adds, “as it is predicted that more than 40 percent of the mass of the universe is in filaments. The combination of overlapping weak lensing, spectroscopic and HI [neutral hydrogen] The survey provides complementary datasets that we can use to fully explore the cosmic web.
