Our universe is home to more “spectacular” polar ring galaxies than previously thought, scientists say

By | September 15, 2023

A team of astronomers has discovered two new potential examples of a strange celestial object known as a polar ring galaxy. This elusive form of galaxy has a ring of stars and gas oriented at 90 degrees to the other stars in the realm, in addition to its main disk.

This result implies that so-called polar rings may not be as rare as scientists suspected.

“Polar ring galaxies are some of the most spectacular-looking galaxies in the universe,” said Nathan Deg, team co-leader and researcher at Queen’s University, Canada. said in a statement. “These results suggest that 1 to 3% of nearby galaxies may have gaseous polar rings, a much higher number than suggested by optical telescopes.”

The strange characteristics of the rings of the two galaxies — NGC 4632, located about 56 million light-years from Earth in the constellation Virgo and NGC 6156, located around 150 million light years far away, in the constellation of Ara, they are hidden in visible light. However, the features revealed themselves in radio observations.

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These weirdos galaxies they are believed to form their own rings stars and gas during mergers in which a larger galaxy engulfs a smaller one, with the gravitational influence of one galaxy pulling a stream of matter from the other. If polar ring galaxies are indeed more common than suspected, this means that these cannibalistic mergers are also more frequent.

Studying polar ring galaxies, which were observed before this discovery, could also help scientists learn more about the dark matter halos that are believed to shroud galaxies as they channel the distribution of matter around them. Dark matter it is a mysterious substance that makes up about 85% of the matter present in the universe but which remains invisible to us.

Therefore, the findings could have significant implications for our understanding of how galaxies grew and, consequently, how the universe It has evolved.

The strange rings of stars and dust around NGC 4632 and NGC 6156 began appearing during an analysis of data collected by the Australian Square Kilometer Array Pathfinder (ASKAP) located in Western Australia.

Jayanne English, a scientist at the University of Manitoba and a member of the discovery team, used optical and infrared data from the Subaru telescope to resolve the spiral disks of NGC 4632 and NGC 6156. English then used radio data from ASKEP’s Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY), which examined the distribution of hydrogen gas around about half million galaxies, to reveal the polar disks around them. It was then that the team realized that ASKAP had detected polar ring galaxies for the first time.

“These results are a great example of the enormous value of mapping the sky deeper and wider than has ever been done before,” Kristine Spekkens, research co-leader and scientist at Queen’s University, said in the statement. “This is serendipity at its best: we found things we certainly didn’t expect to find.”

Composite images of galaxies show details of their rings that human eyes would not be able to see, thanks to the incorporation of light beyond the visible light spectrum, such as the radio light of cold hydrogen.

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“We were able to work with data that showed a fine grid of velocity channels, which are equivalent to the radio stations on your old radio receiver,” English said. “The richness of the velocity data allowed me to assign multiple colors to this composite to subtly convey the motion occurring within the polar ring.”

Color gradients within the rings show the different orbital motion of the gas, with the purple regions at the base of the disk showing areas moving towards Earth, while the white regions at the top of the disk are moving away from us.

“The dance and choreography of the gas is beautiful, and that movement of the gas gives us some clues about how galaxies evolve over time.” time“, concluded the Englishman.

The next step for researchers will be to confirm that these are indeed polar ring galaxies by studying NGC 4632 and NGC 6156 with a wide range of telescopes, including the MeerKAT radio telescope in South Africa.

The team’s findings were published September 13 in the journal Monthly notices of the Royal Astronomical Society.

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