ASKAP reveals the radio tail structure of the Corkscrew Galaxy shaped by its passage through the Abell 3627 cluster

Abstract

Among the bent-tail radio galaxies common in galaxy clusters are some with long, collimated tails (so-called head-tail galaxies) shaped by their interactions with the intracluster medium (ICM). Here, we report the discovery of intricate filamentary structure in and beyond the ∼28 arcmin (570 kpc) long, helical radio tail of the Corkscrew Galaxy (1610–60.5, ESO 137-G007), which resides in the X-ray bright cluster Abell 3627 (D = 70 Mpc). Deep radio continuum data were obtained with wide-field phased array feeds on the Australian Square Kilometer Array Pathfinder (ASKAP) at 944 MHz and 1.4 GHz. While the bright (young) part of the Corkscrew Galaxy tail is highly collimated, the faint (old) part shows increasing oscillation amplitudes, break-ups, and filaments. We find a stunning set of arc-shaped radio filaments beyond and mostly orthogonal to the collimated Corkscrew tail end, forming a partial bubble. This may be the first detection of a ‘proto-lobe’ previously seen in 3D MHD simulations, formed by the face-on impact of the Corkscrew Galaxy with a shock front in the cluster outskirts. Interactions of the radio galaxy tail with the ICM are likely responsible for the tail collimation and shear forces within the ICM for its increasingly filamentary structure. We also report the discovery of small (∼20–30 kpc) ram-pressure stripped radio tails in four Abell 3627 cluster galaxies, located between the Corkscrew Galaxy and its prominent neighbour, the wide-angle tail (WAT) radio galaxy 1610–60.8 (ESO 137-G006).