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Accepted manuscript

Discovery of Odd Radio Circles and Other Peculiars in the First Year of the EMU Survey using Object Detection

Published online by Cambridge University Press:  26 June 2025

Nikhel Gupta Open the ORCID record for Nikhel Gupta [Opens in a new window] ,
Ray P. Norris ,
Zeeshan Hayder ,
Minh Huynh ,
Heinz Andernach ,
Andrew M. Hopkins Open the ORCID record for Andrew M. Hopkins [Opens in a new window] ,
Stanislav Shabala Open the ORCID record for Stanislav Shabala [Opens in a new window] ,
Lawrence Rudnick ,
Miroslav D. Filipović Open the ORCID record for Miroslav D. Filipović [Opens in a new window]  and
Bärbel S. Koribalski Open the ORCID record for Bärbel S. Koribalski [Opens in a new window]
...Show all authors
Nikhel Gupta*
Affiliation:
CSIRO Space & Astronomy, PO Box 1130, Bentley WA 6102, Australia
Ray P. Norris
Affiliation:
Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia CSIRO Space & Astronomy, P.O. Box 76, Epping, NSW 1710, Australia
Zeeshan Hayder
Affiliation:
CSIRO Data61, Black Mountain ACT 2601, Australia
Minh Huynh
Affiliation:
CSIRO Space & Astronomy, PO Box 1130, Bentley WA 6102, Australia International Centre for Radio Astronomy Research (ICRAR), M468, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
Heinz Andernach
Affiliation:
Depto. de Astronomía, DCNE, Universidad de Guanajuato, Cjón. de Jalisco s/n, Guanajuato, CP 36023, Mexico
Andrew M. Hopkins
Affiliation:
School of Mathematical and Physical Sciences, 12 Wally’s Walk, Macquarie University, NSW 2109, Australia
Stanislav Shabala
Affiliation:
School of Natural Sciences, University of Tasmania, Private Bag 37, Hobart 7001, Australia
Lawrence Rudnick
Affiliation:
University of Minnesota, 100 Church St SE, Minneapolis, MN 55455, USA
Miroslav D. Filipović
Affiliation:
Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia
Bärbel S. Koribalski
Affiliation:
Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia CSIRO Space & Astronomy, P.O. Box 76, Epping, NSW 1710, Australia
Lars Petersson
Affiliation:
CSIRO Data61, Black Mountain ACT 2601, Australia
X. Rosalind Wang
Affiliation:
Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia
*
Author for correspondence: Nikhel Gupta, Email: Nikhel.Gupta@csiro.au.
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Abstract

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We present a systematic search for Odd Radio Circles (ORCs) and other unusual radio morphologies using data from the first year of the EMU (Evolutionary Map of the Universe) survey. ORCs are rare, enigmatic objects characterized by edge-brightened rings of radio emission, often found in association with distant galaxies. To identify these objects, we employ a hybrid methodology combining supervised object detection techniques and visual inspection of radio source candidates. This approach leads to the discovery of five new ORCs and two additional candidate ORCs, expanding the known population of these objects. In addition to ORCs, we also identify 55 Galaxies with Large-scale Ambient Radio Emission (GLAREs), which feature irregular, rectangular, or circular shapes of diffuse radio emission mostly surrounding central host galaxies. These GLAREs may represent different evolutionary stages of ORCs, and studying them could offer valuable insights into their evolutionary processes. We also highlight a subset of Starburst Radio Ring Galaxies (SRRGs), which are star-forming galaxies exhibiting edge-brightened radio rings surrounding their central star-forming regions. We emphasize the importance of multi-wavelength follow-up observations to better understand the physical properties, host galaxy characteristics, and evolutionary pathways of these radio sources.

Keywords

galaxies: activegalaxies: peculiarradio continuum: galaxiesGalaxy: evolutionmethods: data analysis

Information

Type
Research Article
Information
Publications of the Astronomical Society of Australia , Accepted manuscript , pp. 1 - 19
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Astronomical Society of Australia