Using the Australian Square Kilometer Array Pathfinder ( ASKAP) instrumentation, astronomers have discovered a new extragalactic exotic radio circle ( ORC). The newly discovered radio source, named ORC J0102-2450, is nearly 1 million light-years in diameter. The discovery was published in a paper in the arXiv preprint.
These strange radio circles ( ORCs) are a mysterious astrophysical phenomenon that has only been discovered in the last year or two. They are very large mysterious objects: highly circular, very massive, and bright along the edges of radio wavelengths.
Although radio circles ( ORCs) are bright at radio wavelengths, they are not observable at visible, infrared or X-ray wavelengths. To date, few objects of this type have been identified, and thus little is known about their origin and nature.
Now, a team of astronomers from the Australian National Telescope, led by B rbel S. Koribalski, reports the latest addition to the short list of known exotic radio circles, ORC J0102-2450, a discovery made as part of a search for ORC and other radio sources in the deep (~40 deg2) ASKAP field centered on the “silver dollar galaxy” NGC 253. Part of the extended radio source: the newly discovered “wave loop” is near it, but not centered on it.
(Image source: ASKAP)
In the paper, the researchers write, “Together with the Australian Square Kilometer Array Pathfinder (ASKAP), we found another strange radio circle (ORC) at 944 MHz.”
The newly discovered ORC radio ring has a diameter of about 70 arc seconds, or 978,000 light years. The total radio flux of the source is measured to be about 3.9 mJy, while its total radio luminosity is about 140 billion TW/Hz. The object is most likely associated with the central elliptical galaxy DES J010224.33-245039.5.
Taking into account the overall radio morphology of ORC J0102-2450 and the undetected ring emission at non-radiometric wavelengths, astronomers have drawn some conclusions about the origin of the ORC. They suggest that it could be the remnant flap of a giant radio galaxy that we see as a “square circle” because we happen to be looking directly above it, or it could be a giant shock wave, possibly from a binary black hole merger of a supermassive black hole, resulting in a radio ring of this size. A third scenario considered by the authors of the paper is that it could be the interaction of radio galaxies and the intergalactic medium ( IGM).
However, the researchers add that more ORC discoveries with ASKAP and other telescopes are needed to test the proposed hypothesis.
In summary, astronomers noted that ORC J0102-2450 with ASKAP makes it the third odd radio circle with elliptical galaxies in its geometric center. They believe that this is not a coincidence: the ORC and such galaxies may go hand in hand, which could help us better understand the formation mechanisms of these sources.
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