Galaxies Align Spin with Cosmic Filaments, Challenging Formation Theories
CAPE TOWN, SOUTH AFRICA – December 6, 2023 - In a revelation reshaping understanding of galaxy formation, astronomers have found that galaxies within a vast cosmic filament are rotating in alignment with the filament’s own rotation, a phenomenon likened to tops spinning with their base. The research, published December 4 in Monthly Notices of the Royal Astronomical Society, suggests a dominant influence of cosmic structure on galactic spin, challenging existing models.
The unprecedented finding stems from observations using the 64 antennas of the MeerKAT radio telescope in South Africa, combined with optical data from the Dark Energy Spectroscopic Instrument (Arizona) and the Sloan Digital Sky Survey (New Mexico).Researchers tracked the movement of neutral hydrogen gas within galaxies and the filaments connecting them.
“What makes this structure unusual is not just its size, but its combination of spin alignment and rotational motion,” explained Lyla Jung of the University of Oxford. ”It can be compared to a teacup ride at an amusement park. Each galaxy is like a spinning cup, while the platform, the cosmic filament, also spins.”
Scientists previously established that filaments within the cosmic web can rotate, based on galactic motion. However, the correlation between filament and galaxy rotation direction is a surprise. Current theories predict galactic spin is often altered by interactions, collisions, and mergers. This new evidence indicates filament rotation may be a primary driver of how galaxies gain rotational momentum.
“These filaments are a fossil record of cosmic flows,” said Madalina Tudorache, also from Oxford, who led the research with Jung. “This helps us understand how galaxies gain spin and grow over time.”
The galaxies observed are relatively young, suggesting their rotations may evolve.The discovery is expected to influence galaxy evolution models and perhaps impact weak lensing surveys used to map dark matter. The Milky Way’s rotation, for example, is attributed to primordial gas clouds from 13 billion years ago.