A unique, ring-like radio source with quadrilateral structure detected with machine learning

Abstract

We report the discovery of a unique object in the MeerKAT Galaxy Cluster Legacy Survey (MGCLS) using the machine learning anomaly detection framework Astronomaly. This strange, ring-like source is 30' from the MGCLS field centred on Abell 209, and is not readily explained by simple physical models. With an assumed host galaxy at redshift 0.55, the luminosity (10^25 W/Hz) is comparable to powerful radio galaxies. The source consists of a ring of emission 175 kpc across, quadrilateral enhanced brightness regions bearing resemblance to radio jets, two "ears" separated by 368 kpc, and a diffuse envelope. All of the structures appear spectrally steep, ranging from -1.0 to -1.5. The ring has high polarization (25%) except on the bright patches (<10%). We compare this source to the Odd Radio Circles recently discovered in ASKAP data and discuss several possible physical models, including a termination shock from starburst activity, an end-on radio galaxy, and a supermassive black hole merger event. No simple model can easily explain the observed structure of the source. This work, as well as other recent discoveries, demonstrates the power of unsupervised machine learning in mining large datasets for scientifically interesting sources.

8 pages, 7 figures, published in MNRAS

References in corpus (14)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• Target Selection and Validation of DESI Luminous Red Galaxies
• Radio interferometric gain calibration as a complex optimization problem
• Convolution kernels for multi-wavelength imaging
• The MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Survey
• Cataloging the radio-sky with unsupervised machine learning: a new approach for the SKA era
• MeerKAT uncovers the physics of an Odd Radio Circle
• The discovery of a radio galaxy of at least 5 Mpc
• Unveiling the rarest morphologies of the LOFAR Two-metre Sky Survey radio source population with self-organised maps
• Unsupervised machine learning for transient discovery in Deeper, Wider, Faster light curves
• Tricolour: an optimized SumThreshold flagger for MeerKAT
• On energetics and progenitors of Odd Radio Circles: A causal connection with tidal disruption of stars?
• The Curious Case of the "Heartworm" Nebula

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