U of M astronomers help citizen scientists discover rare galaxy cluster

June 28, 2016
newly discovered Cluster RGZ-CL

A radio contour overlay showing the newly discovered Cluster RGZ-CL J0823.2+0333.
Credit: Banfield et al./SDSS

Two volunteer participants in an international crowdsourcing research project have discovered a rare galaxy cluster 1.2 billion light years away with help from astronomers at the University of Minnesota.

The two citizen scientists independently noted something suspicious about the radio wave structure in an image shown to them as part of the web-based project, called Radio Galaxy Zoo, where volunteers are asked to help categorize huge numbers of galaxy images that are too numerous for professional astronomers.

Crowdsourcing allows researchers to efficiently and effectively comb through large amounts of data using the public’s help. More than 10,000 citizen scientists have volunteered with Radio Galaxy Zoo, producing more than 1.6 million image classifications from NASA’s Wide-Field Infrared Survey Explorer telescope and the NRAO Very Large Array in New Mexico, USA.

In this case, the volunteers noted that what they saw in the radio wave image seemed to connect with other structures that were beyond the scope of the image they were given. The pair pieced together the huge C-shaped structure from much smaller images of cosmic radio waves. They posted their findings on a chat board for the Radio Galaxy Zoo project.

University of Minnesota Physics and Astronomy Professor Lawrence Rudnick was the first professional astronomer to note their observations.

“I picked up on their posts and started chatting with them online and figured out that what they were looking at was quite interesting. That was the start of the project,” said Rudnick, who is one of the co-authors of the paper. “Their observations intrigued us to look closer and do additional follow-up research, which eventually led to the paper.”

Using additional observations and with insights from video simulations, the astronomers classified the newly-discovered feature as a wide angle tail (WAT) radio galaxy, named for the C-shape formed by the highly energetic jets of plasma which are being ejected from it.

The discovery is part of a previously unreported sparsely populated galaxy cluster and one of the largest WATs ever found. The findings were recently published in the Monthly Notices of the Royal Astronomical Society with the two volunteers included as co-authors. The discovery, named the Matorny-Terentev Cluster RGZ-CL J0823.2+0333, even bears the names of the two citizen scientists.

“I am still amazed and feel more motivated to look for stunning new radio galaxies,” said volunteer Tim Matorny in an article on the Radio Galaxy Zoo website.

For volunteer Ivan Terentev, this isn’t the first time he has made a discovery. He is a co-author on three other papers from findings he made on another citizen science platform, called Planet Hunters. “It is always awesome, like every single time,” he said in an article on the Radio Galaxy Zoo website. “I keep my head cool over that since most of the work was done by the professional scientists.”

The discovery surprised some of the international astronomers involved in Radio Galaxy Zoo.

“They found something that none of us had even thought would be possible,” said Julie Banfield, the lead author of the research paper and researcher at the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) at The Australian National University (ANU).

Rudnick said crowdsourcing research using citizen scientists is a new way to help unlock mysteries of the Universe.

“We continue to need help from the public to help us categorize the hundreds of thousands and soon to be tens of millions of telescope images,” Rudnick said. “Humans are much better at this task than computers and there are just too many images for astronomers and graduate students to research. With citizen science projects like this, a whole new world of research projects is possible.”

In addition to Rudnick, other University of Minnesota co-authors of the research include Professor Tom Jones and former postdoctoral researcher Kyle Willett. Radio Galaxy Zoo is enabled by the crowdsourcing capabilities of Zooniverse, the largest online platform for collaborative volunteer research. Zooinverse was founded by University of Minnesota researchers.

For more information on the research paper entitled “Radio Galaxy Zoo: Discovery of a poor cluster through a giant wide-angel tail radio galaxy,” visit the Monthly Notices of the Royal Astronomical Society website.

In order to understand radio sources like these, researchers at the University of Minnesota created simulations using supercomputers. In this case, they shot two streams of material out from the nucleus of the parent galaxy, and found that a cluster is needed to provide winds that bend the streams into the observed "C" shape.

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