New odd radio circle discovered with MeerKAT telescope

Using the MeerKAT telescope, astronomers have discovered a new odd radio circle that appears to be associated with an elliptical galaxy known as WISEA J021912.43–050501.8. The finding, which could help us better understand the nature of this mysterious radio emission phenomenon, is reported in a paper published Nov. 26 on the arXiv preprint server.

The so-called odd radio circles (ORCs) are mysterious gigantic rings of radio waves and their origin is still unexplained. They are generally observed as extragalactic circles of steep-spectrum radio emission, without any corresponding emission at other wavelengths, other than that of the host galaxy. To date, only several such features have been well-defined as ORCs.

Now, a team of astronomers led by Ray P. Norris of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia, reports the detection of another ORC. The discovery was made as part of the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey—a deep radio survey conducted with the MeerKAT telescope.

“We present the discovery of a new odd radio circle (ORC J0219–0505) in 1.2 GHz radio continuum data from the MIGHTEE survey taken with the MeerKAT,” the researchers wrote in the paper.

The newfound ORC, designated ORC J0219–0505, has been identified as an edge-brightened ring of radio emission surrounding a compact radio source in the center. This ring appears to be filled with faint diffuse emission, with hints of some structure. Moreover, the observations also detected some faint diffuse emission extending to the south-east of the ring.

According to the study, the host galaxy of the new ORC is the massive elliptical galaxy WISEA J021912.43–050501.8, which showcases extended features visible in optical and infrared images. Such extended features are characteristic of disturbance by a merger or interaction, which suggests that ORC J0219–0505 may be a shell of radio emission resulting from electrons energized by a spherical shock from a galaxy merger.

The diameter of ORC J0219–0505 was measured to be 35 arcseconds, which corresponds to 371,600 light years (assuming the host galaxy’s redshift of 0.196), while its width was found to be approximately 107,500 light years.

The researchers noted that ORC J0219–0505 is much smaller and fainter than the previously found single ORCs. They added that the discovery of this ORC in a deep but relatively small-area radio survey indicates that there is a fainter population of ORCs that remains to be unveiled by MeerKAT or other radio telescopes.

The authors of the paper plan further investigation of ORC J0219–0505, which will be focused on its morphological features, polarization and spectral properties. Such a study could be essential to better understand the process that generates ORCs.

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