RG-CAT: Detection Pipeline and Catalogue of Radio Galaxies in the EMU
  Pilot Survey
Nikhel Gupta Ray P. Norris Zeeshan Hayder Minh Huynh Lars Petersson X. Rosalind Wang Andrew M. Hopkins Heinz Andernach Yjan Gordon Simone Riggi Miranda Yew Evan J. Crawford Bärbel Koribalski Miroslav D. Filipović Anna D. Kapinśka Stanislav Shabala Tessa Vernstrom Joshua R. Marvil
We present source detection and catalogue construction pipelines to build the
first catalogue of radio galaxies from the 270 $\rm deg^2$ pilot survey of the
Evolutionary Map of the Universe (EMU-PS) conducted with the Australian Square
Kilometre Array Pathfinder (ASKAP) telescope. The detection pipeline uses
Gal-DINO computer-vision networks (Gupta et al., 2024) to predict the
categories of radio morphology and bounding boxes for radio sources, as well as
their potential infrared host positions. The Gal-DINO network is trained and
evaluated on approximately 5,000 visually inspected radio galaxies and their
infrared hosts, encompassing both compact and extended radio morphologies. We
find that the Intersection over Union (IoU) for the predicted and ground truth
bounding boxes is larger than 0.5 for 99% of the radio sources, and 98% of
predicted host positions are within $3^{\prime \prime}$ of the ground truth
infrared host in the evaluation set. The catalogue construction pipeline uses
the predictions of the trained network on the radio and infrared image cutouts
based on the catalogue of radio components identified using the Selavy source
finder algorithm. Confidence scores of the predictions are then used to
prioritize Selavy components with higher scores and incorporate them first into
the catalogue. This results in identifications for a total of 211,625 radio
sources, with 201,211 classified as compact and unresolved. The remaining
10,414 are categorized as extended radio morphologies, including 582 FR-I,
5,602 FR-II, 1,494 FR-x (uncertain whether FR-I or FR-II), 2,375 R (single-peak
resolved) radio galaxies, and 361 with peculiar and other rare morphologies. We
cross-match the radio sources in the catalogue with the infrared and optical
catalogues, finding infrared cross-matches for 73% and photometric redshifts
for 36% of the radio galaxies.