Discoveries of giant radio galaxies demonstrating the power of low surface brightness, wide-field imaging at high resolution

We present the discovery of 15 well-resolved giant radio galaxies (GRGs) with angular sizes ≥5 arcmin and physical sizes >1 Mpc in wide-field Phased Array Feed 944 MHz observations on the Australian Square Kilometre Array Pathfinder (ASKAP).We identify their host galaxies, examine their radio properties as well as their environment, and classify their morphologies as FR I (4), FR II (8), intermediate FR I/II (2), and hybrid (1). The combined ∼40 deg² ASKAP image of the Sculptor field, which is centred near the starburst galaxy NGC 253, has a resolution of 13′′ and an rms sensitivity of ≳10 μJy beam^–1. The largest GRGs in our sample are ASKAP J0057–2428 (z_phot = 0.238), ASKAP J0059–2352 (z_phot = 0.735) and ASKAP J0107–2347 (z_phot = 0.312), for which we estimate linear projected sizes of 2.7, 3.5 and 3.8 Mpc, respectively. In total we catalog 232 extended radio galaxies of which 77 (33%) are larger than 0.7 Mpc and 35 (15%) are larger than 1 Mpc. The radio galaxy densities are 5.8 deg^–2 (total) and 0.9 (1.9) deg^–2 for those larger than 1 (0.7) Mpc, similar to previous results. Furthermore, we present the ASKAP discovery of a head-tail radio galaxy, a double-lobe radio galaxy with a spiral host, and radio emission from several galaxy clusters. As the ASKAP observations were originally conducted to search for a radio counterpart to the gravitational wave detection GW190814 (z ∼ 0.05), we highlight possible host galaxies in our sample.