Original Published Date: 
Friday, November 29, 2019

Full article issued by the ARC Centre of Excellence for All Sky Astrophysics in 3D (ASTRO 3D).

The direction in which a galaxy spins depends on its mass, ARC-supported researchers have found.

A team of astrophysicists analysed 1418 galaxies and found that small ones are likely to spin on a different axis to large ones. The rotation was measured in relation to each galaxy’s closest 'cosmic filament'—the largest structures in the universe.

Filaments are massive thread-like formations, comprising huge amounts of matter—including galaxies, gas and, modelling implies, dark matter. They can be 500 million light years long, but just 20 million light years wide. At their largest scale, the filaments divide the universe into a vast gravitationally linked lattice interspersed with enormous dark matter voids.

Using data gathered by an instrument called the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) at Australia’s Anglo-Australian Telescope (AAT), ASTRO 3D researchers Dr Charlotte Welker, and ARC Laureate Fellow, Professor Joss Bland-Hawthorn, as well as colleagues from around Australia, the US, France and Korea studied each of the target galaxies and measured its spin in relation to its nearest filament.

They found that smaller ones tended to rotate in direct alignment to the filaments, while larger ones turned at right angles. The alignment changes from the first to the second as galaxies, drawn by gravity towards the spine of a filament, collide and merge with others, thus gaining mass.

Photo credit: 

A simulation showing a section of the Universe at its broadest scale. A web of cosmic filaments forms a lattice of matter, enclosing vast voids. Credit: Tiamat simulation, Greg Poole.