Aren’t polar ring galaxies so rare after all?

Queen’s researchers lead the discovery of two potential polar ring galaxies.

A group of international astronomers, including researchers from Queen’s University, have identified two possible polar galaxies, according to results published September 13 in the journal Monthly Notices of the Royal Astronomical Society.

Queen’s researchers Nathan Deeg and Christine Speakens (Physics, Engineering Physics and Astronomy) led the analysis of data obtained using a telescope owned and operated by Queen’s University. CSIROAustralian National Science Agency. Looking at sky maps of hydrogen gas in more than 600 galaxies as part of CSIRO’s ASKAP radio telescope Wallaby scanThey identified two possible polar ring galaxies, a type of galaxy that exhibits a ring of stars and gas perpendicular to its main spiral disk.

“Polar ring galaxies are some of the most fascinating galaxies in the universe. These results suggest that between 1 and 3 percent of nearby galaxies may contain gaseous polar rings, a much higher percentage than suggested by optical telescopes.”

— Dr. Nathan Deeg, researcher, Department of Physics, Engineering Physics and Astronomy, Queen’s University, Canada, and lead author of the study

Historical context and implications

Although this is not the first time astronomers have observed polar ring galaxies, it is the first time they have been observed using the ASKAP telescope located at Inyarrimanha Ilgari Bundara, CSIRO’s Murchison radio astronomy observatory on the Wajarri Yamaji District in Western Australia.

These new discoveries in gas alone suggest that polar ring galaxies may be more common than previously thought.

“These results are a truly remarkable example of the enormous value of mapping the sky deeper and wider than has been done before. This is serendipity at its best: we have found things that we definitely did not expect to find.”

— Dr Christine Speakens, Professor (Royal Military College Appointed), Department of Physics, Engineering Physics and Astronomy, Queen’s University, Canada

Understand how galaxies evolve

Further research into the structures of the polar rings could help us better understand how galaxies evolve. For example, one of the main hypotheses to explain the origin of polar rings is the merger of a larger galaxy engulfing a smaller galaxy. If polar ring galaxies are more common than previously thought, this could mean that such mergers are more frequent.

In the future, polar ring galaxies could also be used to deepen our understanding of the universe, with potential applications in dark matter research. The polar rings could be used to probe the shape of the host galaxy’s dark matter, which could lead to new clues about the mysterious properties of the elusive matter.

“These new observations from ASKAP, which reveal striking ring-like structures around seemingly normal spiral galaxies, suggest that gas accretion through interactions with gas-rich companion galaxies is much more common than we previously thought. Wallaby will be a great resource for detecting more These systems in the future.

— Professor Lester Staveley-Smith, co-principal investigator and interim CEO of WALLABY. Repeat

Visualization of polar ring galaxies

Jayanne English, a member of the WALLABY research team and also an astronomical image-making expert at the University of Manitoba, developed the first images of these gaseous polar ring galaxies using a combination of optical and radio data from different telescopes. First, optical and infrared data from the Subaru Telescope in Hawaii provided an image of the galaxy’s spiral disk. Next, the gaseous ring was added based on data obtained from the WALLABY survey, an international project that uses CSIRO’s ASKAP radio telescope to detect the emission of atomic hydrogen from about half a million galaxies.

“Our ASKAP radio telescope is delivering a torrent of data and we are ready for it. With ASKAP, a full WALLABY will provide more than 200,000 hydrogen-rich galaxies, including many unusual objects such as the polar rings, which can be used to explore the shape and distribution of dark matter halos.”

— Dr. Barbel Korybalski, Senior Principal Research Scientist, CSIRO

The creation of this and other astronomical images is complex because it includes information that our eyes cannot capture. In this particular case, the cold hydrogen gas component, invisible to the human eye, can be seen in radio “light” using CSIRO’s ASKAP. The subtle hue of this ring represents the orbital movements of the gas, with purple tints at the bottom tracking the gas moving toward the viewer as the top moves away. Emissions from the ring were separated from radio emissions from the galactic disk using virtual reality tools, in collaboration with Professor Tom Garrett (University of Cape Town, South Africa).

“I’m excited to work with such a diverse and collaborative team. We were able to work with data that showed a precise network of velocity channels, which are the equivalent of the radio stations on your old radio receiver. The richness of the velocity data meant I could assign multiple colors to this composite to convey The movement that occurs inside the polar ring is subtly The dance and design of the gas is beautiful, and the movement of the gas gives us some clues about how galaxies evolve over time.

— Dr.. Jayann English, Department of Physics and Astronomy, University of Manitoba

More than 25 global collaborators from Canada, Australia, South Africa, Ecuador, Burkina Faso, Germany, China and others worked together to analyze data from the first public data release of the WALLABY survey, resulting in the newly published paper.

The team’s next step is to confirm the discovery of polar ring galaxies through additional observations using various telescopes, including the MeerKAT radio telescope in South Africa.

“One of the most exciting results of a large survey like the WALLABY survey, which will scan most of the southern sky to make the largest census of neutral atomic hydrogen ever, is the discovery of the unexpected – these unusual galaxies with beautiful rings of gas are absolutely perfect examples of this.”

— Assistant Professor Barbara Catinella, co-principal investigator of WALLABY and co-author of this study. ICRAR, University of Western Australia

Reference: “WALLABY experimental survey: possible polar ring galaxies NGC 4632 and NGC 6156″ by N Deg, R Palleske, K Spekkens, J Wang, T Jarrett, J English, X Lin, J Yeung, JR Mold, B Catinella, H Dénes, A Elagali, B -Q For, P Kamphuis, BS Koribalski, K Lee-Waddell, C Murugeshan, S Oh, J Rhee, P Serra, T Westmeier, OI Wong, K Bekki, A Bosma, C Carignan, BW Holwerda and N. Yu, September 13, 2023, Monthly Notices of the Royal Astronomical Society.
doi: 10.1093/manras/stad2312