Researchers have identified a “razor-thin” string of 14 neutral hydrogen-rich (HI) galaxies, about 5.5 million light-years long and 117 light-years wide, embedded within a much larger filament about 50 million light-years long and containing more than 280 galaxies; the researchers have uncovered unexpected alignments that challenge models of how galaxies get their spin.
An international research team has discovered one of the largest rotating structures ever recorded: a "razor-thin" chain of galaxies located within a massive, swirling cosmic filament 140 million light-years from Earth. The discovery may help clarify how galaxies first evolved in the early universe.
Cosmic filaments are the largest known structural formations in the universe. They consist of vast, thread-like networks of galaxies and dark matter that form a kind of cosmic framework. These structures also direct matter and momentum toward nearby galaxies.
When nearby filaments have many galaxies rotating in the same direction, and when the entire filament appears to be rotating as a whole, they provide rare opportunities to examine how galaxies achieved their current rotation and gas content. They also allow scientists to test ideas about how large-scale cosmic rotation was created over tens of millions of light-years.
A very thin string of galaxies within a massive filament
In the new study, the researchers identified 14 hydrogen-rich galaxies arranged in a long, narrow structure about 5.5 million light-years long and 177,000 light-years wide. This thin array is located within a much larger filament that spans about 50 million light-years and contains more than 280 other galaxies.
Many galaxies in this region appear to be rotating in the same direction as the filament itself, much more frequently than we would expect from a random direction. This pattern challenges existing models and suggests that large cosmic structures may shape the rotation of galaxies more strongly, or for longer periods, than previously understood.
The researchers found that the galaxies on either side of the filament are moving in opposite directions, suggesting that the entire structure is rotating. Using models of filament dynamics, they inferred a rotation speed of 110 kilometers per second and estimated that the radius of the dense region of the filament is about 50 kiloparsecs (about 163,000 light-years).
Insights into galaxy rotation and cosmic dynamics
Dr Leila Jung, one of the authors, said: "This structure is extraordinary not only because of its size but also because of the combination of coordinated spin and rotational motion. It's like a teacup coaster at an amusement park. Each galaxy is like a spinning teacup, but the whole platform – the cosmic filament – is also spinning. This dual motion gives us rare insights into how galaxies get their spin from the larger structures they reside in."
The filament appears to be a relatively young and undisturbed structure. The large number of gas-rich galaxies and the low internal motion – a condition called "dynamical cold" – suggest that it is still in an early stage of development.
Hydrogen is the raw material for star formation, so galaxies that contain a lot of hydrogen are actively collecting or storing fuel for star formation. Studying these galaxies can therefore provide a window into early or ongoing stages of galaxy evolution.
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One response
In space, the concept of "galaxies rotating in the same direction" has no fundamental meaning because it is a matter of planar symmetry (depending on which side the direction of rotation is viewed from), and in any case, the "angular momentum" of a body depends on the mutual interaction between countless massive bodies in space.