Discovery of A Large-scale Bent Radio Jet in the Merging Cluster A514

Abstract

We report a discovery of a large-scale bent radio jet in the merging galaxy cluster A514 (z = 0.071). The radio emission originates from the two radio lobes of the active galactic nucleus (AGN) located near the center of the southern subcluster and extends toward the southern outskirts with multiple bends. Its peculiar morphology is characterized by a 400 kpc “bridge,” a 300 kpc “arc,” and a 400 kpc “tail,” which together contribute to its largest linear size of ∼0.7 Mpc. We find that both the flux and spectral features of the emission change with the distance from the AGN. Also, the “bridge” presents a 60% polarized radio emission, which coincided with an X-ray cold front. Based on our multiwavelength observations, we propose that A514 presents a clear case for the redistribution of an old AGN plasma due to merger-driven gas motions. We support our interpretation with idealized cluster merger simulations employing a passive tracer field to represent cosmic-ray electrons and find that merger-driven motions can efficiently create a cloud of these particles in the cluster outskirts, which later can be reaccelerated by the cluster merger shock and produce radio relics.

The Seeding of Cosmic Ray Electrons by Cluster Radio Galaxies: A Review

“…Nowadays, radio and X-ray observations are providing clear evidence of this kind of interaction in many clusters (Figure 1). Shocks or cold fronts co-located with sudden direction changes of radio galaxy tails have been reported in Abell 3411 [77], Coma [78], Abell 3376 [79], Abell 1775 [49], Abell 3562 [80], Abell 514 [37], and are invoked in other cases to explain the disturbed morphology of the radio emission [81][82][83][84]. Shocks can re-energize cosmic ray electrons both via re-acceleration (Fermi I processes) and adiabatic compression, e.g., [85][86][87].…”

“…Shocks can re-energize cosmic ray electrons both via re-acceleration (Fermi I processes) and adiabatic compression, e.g., [85][86][87]. Shear flows inside cold fronts stretch and amplify magnetic fields, e.g., [79,88], possibly dragging the relativistic plasma with them in tangential directions, e.g., [19,37,79,80,84,89]. Turbulence, either induced by cluster-cluster mergers or by sloshing or by the wake of a fast-moving radio galaxy, can trigger Fermi II re-acceleration mechanisms [90][91][92][93][94].…”

“…Figure 1.Examples of ongoing cosmic ray seeding and interaction between radio galaxies and thermal gas. From top left to bottom right: AGN with bent radio tails (green) due to the interaction with the X-ray gas (purple) in Abell 514[37]; radio plasma (red) transported by thermal gas (blue) sloshing motions in the NGC 507 group[19]; the filamentary radio phoenix in Abell 85[38]; the complex system of filamentary-tailed radio AGN (red) at the center of Abell 2255[39]; the radio phoenix and the long head-tail radio galaxy in Abell 2256[40]; and a radio galaxy feeding the radio relic in the Coma cluster[41].…”