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

Abstract

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.

19 pages, 7 figures, 6 tables. Accepted for publication in PASA

References in corpus (17)

• Observational Signatures of Galactic Winds Powered by Active Galactic Nuclei
• WISE x SuperCOSMOS photometric redshift catalog: 20 million galaxies over 3pi steradians
• All-purpose, all-sky photometric redshifts for the Legacy Imaging Surveys Data Release 8
• The Dark Energy Camera Plane Survey 2 (DECaPS2): More Sky, Less Bias, and Better Uncertainties
• Discovery of a new extragalactic circular radio source with ASKAP: ORC J0102-2450
• Unveiling the rarest morphologies of the LOFAR Two-metre Sky Survey radio source population with self-organised maps
• A Uniformly Selected, All-Sky, Optical AGN Catalog
• A unique, ring-like radio source with quadrilateral structure detected with machine learning
• Insights on the origin of ORCs from cosmological simulations
• Photometric redshifts and Galaxy Clusters for DES DR2, DESI DR9, and HSC-SSP PDR3 Data
• Fokker-Planck Models for M15 without a Central Black Hole: The Role of the Mass Function
• A Multimodal Dataset and Benchmark for Radio Galaxy and Infrared Host Detection
• Enabling Unsupervised Discovery in Astronomical Images through Self-Supervised Representations
• Yet another Odd Radio Circle?
• Discovery of a circularly symmetric extended diffuse radio emission around an elliptical galaxy with the VLA FIRST survey
• A horseshoe-shaped ring of diffuse emission detected at 1.4 GHz
• Self-Supervised Learning on MeerKAT Wide-Field Continuum Images

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• Cosmological Zoom-In Simulation of Odd Radio Circles as Merger-Driven Shocks in Galaxy Groups
• MeerKAT discovery of 164 compact radio rings toward the Galactic Plane
• RAD@home discovery of a bow-and-arrow radio galaxy tracing a ~560 kpc bow-shock structure in a multi-halo environment
• Deep polarimetry study reveals double ring ORC-like structures