Rare and beautiful polar ring galaxies discovered by ASKAP

Astronomers have revealed the discovery of two potential polar ring galaxies, NGC 4632 and NGC 6156.

In a study published yesterday in the Monthly Notices of the Royal Astronomical Society, the research team, led by Canada’s Queens University-based astrophysicist Nathan Deg, explained that the discovery was made while analyzing data from the Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY).

The WALLABY leads the search

The WALLABY is a next-generation survey running on the Australian Square Kilometre Array Pathfinder (ASKAP), a radio telescope in Western Australia.

According to Deg, “finding two potential polar ring galaxies in the Wallaby pilot survey is incredibly exciting, as it suggests that these objects may be more common than previously thought”.

“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,’’ he added.

Where are these polar ring galaxies?

The NGC 4632 galaxy lies 56 million light-years away and is surrounded by a hydrogen gas ring only detectable by radio telescopes. It was initially noticed in a 2022 WALLABY survey when the team explored the movement of the mass of gas around the galaxy.

The NGC 6156 galaxy has a less prominent ring and is located about 150 million light-years away. The researchers examined the speed of the gas encircling the galaxy and are less certain that it could be a polar ring.

ASKAP holds great potential

Professor Bärbel Koribalski, an astronomer at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), was a co-author of the report. She underscored the great potential and powers of the ASKAP. 

‘’NGC 4632 is one of two polar ring galaxies we’ve identified from 600 galaxies that were mapped in our first small WALLABY survey.’’

‘’The two polar ring galaxies are just the beginning of a huge project. 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.’’

Next up in the hunt for polar ring galaxies

While the these galaxies are waiting to be confirmed, the researchers predict that further studies of the NGC 4632 and NGC 6156 may open the floodgates for finding many similar galaxies in the future. 

‘’As better observations and more sophisticated models are obtained for both galaxies, it will be possible to constrain the parameters of the ring progenitor (if they are indeed formed via mergers or flybys).’’

Scientists categorize galaxies into 4 main types— spiral, elliptical, lenticular, and irregular. Lenticular galaxies (denoted S0) are the most well-known polar ring galaxies. NGC 2685, NGC 4650A, A 0136 -0801, and ESO 415 -G26 were the first four S0 galaxies recognized as polar ring galaxies.

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