TY - JOUR
T1 - Ionized Gas Extended Over 40 kpc in an Odd Radio Circle Host Galaxy
AU - Coil, Alison L.
AU - Perrotta, Serena
AU - Rupke, David S. N.
AU - Lochhaas, Cassandra
AU - Tremonti, Christy A.
AU - Diamond-Stanic, Aleks
AU - Fielding, Drummond
AU - Geach, Jim
AU - Hickox, Ryan C.
AU - Moustakas, John
AU - Rudnick, Gregory H.
AU - Sell, Paul
AU - Whalen, Kelly E.
N1 - © 2024, The Author(s), under exclusive licence to Springer Nature Limited. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1038/s41586-023-06752-8
PY - 2024/1/8
Y1 - 2024/1/8
N2 - A new class of extragalactic astronomical sources discovered in 2021, named Odd Radio Circles (ORCs, Norris et al. 2021), are large rings of faint, diffuse radio continuum emission spanning ~1 arcminute on the sky. Galaxies at the centers of several ORCs have photometric redshifts of z~0.3-0.6, implying physical scales of several 100 kiloparsecs in diameter for the radio emission, the origin of which is unknown. Here we report spectroscopic data on an ORC including strong [OII] emission tracing ionized gas in the central galaxy of ORC4 at z=0.4512. The physical extent of the [OII] emission is ~40 kpc in diameter, larger than expected for a typical early-type galaxy (Pandya et al, 2017) but an order of magnitude smaller than the large-scale radio continuum emission. We detect a ~200 km/s velocity gradient across the [OII] nebula, as well as a high velocity dispersion of ~180 km/s. The [OII] equivalent width (EW, ~50 Ang) is extremely high for a quiescent galaxy. The morphology, kinematics, and strength of the [OII] emission are consistent with the infall of shock ionized gas near the galaxy, following a larger-scale, outward moving shock driven by a galactic wind. Both the extended optical and radio emission, while observed on very different scales, may therefore result from the same dramatic event.
AB - A new class of extragalactic astronomical sources discovered in 2021, named Odd Radio Circles (ORCs, Norris et al. 2021), are large rings of faint, diffuse radio continuum emission spanning ~1 arcminute on the sky. Galaxies at the centers of several ORCs have photometric redshifts of z~0.3-0.6, implying physical scales of several 100 kiloparsecs in diameter for the radio emission, the origin of which is unknown. Here we report spectroscopic data on an ORC including strong [OII] emission tracing ionized gas in the central galaxy of ORC4 at z=0.4512. The physical extent of the [OII] emission is ~40 kpc in diameter, larger than expected for a typical early-type galaxy (Pandya et al, 2017) but an order of magnitude smaller than the large-scale radio continuum emission. We detect a ~200 km/s velocity gradient across the [OII] nebula, as well as a high velocity dispersion of ~180 km/s. The [OII] equivalent width (EW, ~50 Ang) is extremely high for a quiescent galaxy. The morphology, kinematics, and strength of the [OII] emission are consistent with the infall of shock ionized gas near the galaxy, following a larger-scale, outward moving shock driven by a galactic wind. Both the extended optical and radio emission, while observed on very different scales, may therefore result from the same dramatic event.
U2 - 10.1038/s41586-023-06752-8
DO - 10.1038/s41586-023-06752-8
M3 - Article
SN - 0028-0836
VL - 625
SP - 459
EP - 462
JO - Nature
JF - Nature
ER -