Spring 2023 ASKAP update

Astronomers reveal ribbons of gas around galaxies

Polar ring galaxies are some of the rarest and most spectacular looking galaxies in the Universe, however an international group of astronomers from ASKAP’s WALLABY survey team think they might be more common than we believe.

a spiral galaxy is surrounded but a white halo of gas. A black background studded with galaxies.
Data obtained from ASKAP combined with optical and infrared data from the Subaru telescope in Hawaii, makes a dramatic composite image of NGC 4632. Credit: J. English (U.Manitoba), with support of T. Jarrett (UCT) and the WALLABY team: ATNF/ASKAP:Suburu/Hyper Suprime Camera
Dr Jayanne English, an expert in astronomy image-making at the University of Manitoba, combined data obtained from ASKAP with optical and infrared data from the Subaru telescope in Hawaii to make the dramatic composite image of NGC 4632. Credit: J. English (U.Manitoba), with support of T. Jarrett (UCT) and the WALLABY team: ATNF/ASKAP:Suburu/Hyper Suprime Camera

The international research team, with many members based in Canada, said the findings suggest one to three per cent of nearby galaxies may have gaseous polar rings, which is much higher than suggested by optical telescopes.

The galaxy in the picture is referred to as NGC 4632. It is 56 million light years from Earth surrounded by a ring of hydrogen gas, stretching like a delicate ribbon made of cosmic dust, gas and stars. The gas ring orbits the galaxy at right angles to its spiral disk and can only be seen by using highly sensitive instruments like our ASKAP radio telescope.

NGC 4632 is one of two polar ring galaxies identified from 600 galaxies in the first small WALLABY survey. Using ASKAP over the coming years, the team expects to reveal more than 200,000 galaxies, including many with polar rings.

Ring, ring!

Why polar rings exist is still a puzzle to astronomers. One possible explanation is that their stellar rings, which appear blended with gas clouds, are shredded material from a passing galaxy. And if polar ring galaxies are more common than previously thought, it could mean that this galactic cannibalism happens more often than realised.

In the future, polar ring galaxies could be used to deepen our understanding of the Universe, with potential applications in dark matter research. It is possible to use polar rings to probe the shape of dark matter of the host galaxy, which could lead to new clues about the mysterious properties of the elusive substance.

The discovery is a good illustration of the tremendous value of mapping the sky more deeply and more widely than has ever been done before. Researchers are finding things they certainly didn’t expect, which keeps the world of astronomy science very interesting indeed.

A radio telescope dish points into a starry sky.
An ASKAP radio telescope dish. Can you spot six others in the background? Credit: CSIRO/Alex Cherney

Aidan Hotan, ASKAP Principal Research Scientist, CSIRO

James Chesters, ATNF Communications Advisor, CSIRO