Surprising Insights: Are Polar Ring Galaxies More Common Than Previously Thought?

Image Credit: NGC 4632, a potential polar ring galaxy showing a ring of gas oriented perpendicularly to the galaxy’s main spiral disk. Source: Jayanne English (University of Manitoba), Nathan Deg (Queen’s University) & WALLABY Survey, CSIRO / ASKAP, NAOJ / Subaru Telescope

A collaborative effort among international astronomers, which includes scientists from Queen’s University, has led to the identification of two candidate polar ring galaxies. The findings were published on September 13 in the scientific journal, Monthly Notices of the Royal Astronomical Society.

Nathan Deg and Kristine Spekkens, both affiliated with the Departments of Physics, Engineering Physics & Astronomy at Queen’s University, spearheaded the analysis. Data for the study were gathered using a telescope operated by CSIRO, Australia’s national science agency. The data consisted of hydrogen gas sky maps from over 600 galaxies and were part of CSIRO’s ASKAP radio telescope’s WALLABY survey. The researchers identified two galaxies that potentially possess a ring of stars and gas oriented perpendicularly to their main spiral disks.

Dr. Nathan Deg, the lead author of the study, stated, “These polar ring galaxies are visually striking celestial bodies. Our findings indicate that between one and three percent of nearby galaxies may possess such gaseous polar rings, a frequency much greater than what optical telescopes had suggested.”

Historical Context and Ramifications

While polar ring galaxies have been observed in the past, these are the first such instances recorded using the ASKAP telescope situated at Inyarrimanha Ilgari Bundara, which is part of CSIRO’s Murchison radio astronomy observatory located in Wajarri Yamaji Country in Western Australia. These new observations, based solely on gas detections, imply that polar ring galaxies may be more prevalent than was previously assumed.

Dr. Kristine Spekkens, a professor with a cross-appointment from the Royal Military College, remarked, “The extensive and deep sky mapping conducted has serendipitously led us to discover features we did not anticipate, thus underscoring the tremendous value of this kind of exploration.”

Unveiling Galactic Evolution

Further study of these polar ring structures could provide valuable insights into the evolution of galaxies. A prevalent theory suggests that polar rings form when a larger galaxy absorbs a smaller one. If polar ring galaxies are indeed more common, this might indicate that such galactic mergers occur more frequently.

In addition, polar ring galaxies offer a new avenue for researching dark matter. They could potentially be used to investigate the shape and properties of the host galaxy’s dark matter.

Professor Lister Staveley-Smith, WALLABY Co-Principal Investigator and Interim Executive Director at ICRAR, noted, “The WALLABY survey is expected to be a significant resource for uncovering more such galaxies and complex systems in the future.”

Advanced Imaging Techniques

Jayanne English, a team member of the WALLABY research project and an expert in astronomical imaging at the University of Manitoba, crafted the first visuals of these gas-encompassed polar ring galaxies. She integrated optical and radio data from various telescopes, including the Subaru telescope in Hawaii for the spiral disk image and WALLABY data for the gaseous ring.

Dr. Bärbel Koribalski, Senior Principal Research Scientist at CSIRO, stated, “Our ASKAP radio telescope is generating an immense volume of data that will help in discovering numerous hydrogen-rich galaxies, including more peculiar structures like polar rings.”

Over two dozen collaborators from multiple countries participated in analyzing the data from WALLABY’s first public data release, culminating in the publication of the study. The team plans to corroborate these findings through additional observations, including usage of the MeerKAT radio telescope in South Africa.

Assistant Professor Barbara Catinella, WALLABY Co-Principal Investigator and co-author of the study, concluded, “One of the most exhilarating results from comprehensive surveys like WALLABY is stumbling upon the unexpected. These unusual galaxies with exquisite gaseous rings exemplify this phenomenon.”

Reference: “WALLABY pilot survey: The potential polar ring galaxies NGC 4632 and NGC 6156” by N Deg, R Palleske, K Spekkens, et al., published in Monthly Notices of the Royal Astronomical Society on 13 September 2023. DOI: 10.1093/mnras/stad2312

Frequently Asked Questions (FAQs) about polar ring galaxies

More about polar ring galaxies

• Monthly Notices of the Royal Astronomical Society
• Queen’s University Departments of Physics, Engineering Physics & Astronomy
• CSIRO’s ASKAP radio telescope
• WALLABY Survey
• MeerKAT radio telescope
• University of Manitoba Department of Physics and Astronomy
• Subaru Telescope
• Dark Matter Research