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

TL;DR

This paper reports the discovery of new Odd Radio Circles and other peculiar radio sources in the EMU survey using a hybrid detection approach, providing insights into their nature and evolution.

Contribution

It introduces a combined supervised detection and visual inspection method that led to discovering five new ORCs and other unusual radio morphologies in the EMU survey.

Findings

Discovered five new ORCs and two candidates.

Identified 55 GLAREs with irregular radio shapes.

Highlighted potential evolutionary links among radio peculiar objects.

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.