International astronomers using a telescope owned and operated by CSIRO, Australia’s national science agency, have revealed a galaxy wrapped in a cosmic ‘ribbon’.
The research, led by Dr Nathan Deg and Dr Kristine Spekkens from Queen’s University Canada and co- authored by CSIRO’s Professor Bärbel Koribalski, presents a stunning image of a galaxy called NGC 4632 that is 56 million light years from Earth.
It’s been identified as a potential polar ring galaxy, which are some of the most spectacular types of galaxies in the Universe, and among the most mysterious.
Detected using CSIRO’s ASKAP radio telescope on Wajarri Yamaji Country in Western Australia, the galaxy features a ring of gas that can only be seen at radio wavelengths. The ring is orbiting the galaxy at right angles to its spiral disk, like a parcel wrapped in a ribbon of cosmic gas, dust and stars. Dr Nathan Deg co-authored the paper published today in Monthly Notices of the Royal Astronomical Society.
“The findings suggest that one to three per cent of nearby galaxies may have gaseous polar rings, which is much higher than suggested by optical telescopes. Polar ring galaxies might be more common than previously thought,” Dr Deg said.
“While this is not the first time astronomers have observed polar ring galaxies, NGC 4632 is the first observed with ASKAP and there may be many more to come,”
Professor Koribalski said the WALLABY survey aims to observe the whole southern sky using ASKAP to detect and visualise the gas distribution in hundreds of thousands of galaxies.
“NGC 4632 is one of two polar ring galaxies we’ve identified from 600 galaxies that were mapped in our first small WALLABY survey.
“Using ASKAP over coming years we expect to reveal more than 200,000 hydrogen-rich galaxies, among them many more unusual galaxies like these ones with polar rings,” Professor Koribalski said.
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.
Another possibility is that hydrogen gas flows along the filaments of the cosmic web and accretes into a ring around a galaxy, possibly forming stars during this process.
Associate Professor Barbara Catinella, from ICRAR’s UWA node, is WALLABY Co-Principal Investigator and co-author on the paper.
“One of the most exciting outcomes of a large survey such as WALLABY, which will scan most of the Southern sky to carry out the largest census of neutral atomic hydrogen ever done, is discovering the unexpected,” she says.
“These unusual galaxies with beautiful gas rings are perfect examples of this.”
In the future, polar ring galaxies can also 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.
Over 25 global collaborators from Canada, Australia, South Africa, Ecuador, Burkina Faso, Germany, China, and beyond worked together to analyse data from the first WALLABY survey collected using ASKAP and processed by the Pawsey Supercomputing Research Centre in Western Australia.
ASKAP is part of CSIRO’s Australia Telescope National Facility. It is also a precursor to the international SKA telescopes currently being built in Australia and South Africa.