`Zwicky's Nonet': a compact merging ensemble of nine galaxies and 4C 35.06, a peculiar radio galaxy with dancing radio jets

TL;DR

This study investigates the peculiar radio galaxy 4C 35.06 within galaxy cluster Abell 407, revealing complex jet structures, relic radio lobes, and a unique nine-galaxy ensemble indicative of a precursor to a multiple-nucleus cD galaxy, highlighting black hole mergers and jet dynamics.

Contribution

It presents multi-frequency radio observations of 4C 35.06, uncovering ultra-steep spectrum relic lobes and a unique galaxy ensemble, providing insights into jet life-cycle and black hole merger physics in dense environments.

Findings

Detection of 400 kpc scale twisted radio jets and relic lobes.

Identification of a nine-galaxy ensemble resembling a precursor to a cD galaxy.

Evidence for jet precession caused by black hole interactions.

Abstract

We report the results of our radio, optical and infra-red studies of a peculiar radio source 4C~35.06, an extended radio-loud AGN at the center of galaxy cluster Abell 407 ($z=0.047$). The central region of this cluster hosts a remarkably tight ensemble of nine galaxies, the spectra of which resemble those of passive red ellipticals, embedded within a diffuse stellar halo of $\sim$1~arcmin size. This system (named the `Zwicky's Nonet') provides unique and compelling evidence for a multiple-nucleus cD galaxy precursor. Multifrequency radio observations of 4C~35.06 with the Giant Meterwave Radio Telescope (GMRT) at 610, 235 and 150 MHz reveal a system of 400~kpc scale helically twisted and kinked radio jets and outer diffuse lobes. The outer extremities of jets contain extremely steep spectrum (spectral index -1.7 to -2.5) relic/fossil radio plasma with a spectral age of a few$\,\times (10^7 - 10^8)$ yr. Such ultra-steep spectrum relic radio lobes without definitive hot-spots are rare, and they provide an opportunity to understand the life-cycle of relativistic jets and physics of black hole mergers in dense environments. We interpret our observations of this radio source in the context of the growth of its central black hole, triggering of its AGN activity and jet precession, all possibly caused by galaxy mergers in this dense galactic system. A slow conical precession of the jet axis due to gravitational perturbation between interacting black holes is invoked to explain the unusual jet morphology.