Speaker
Description
Context: The latest generation of radio telescopes, with their enhanced sensitivity and refined spatial resolution, are unveiling previously unidentified objects and capturing them with unprecedented details. One such enigmatic object is a radio galaxy located within the Abell 3266 cluster named "MysTail", observed as part of the MeerKAT Galaxy Cluster Legacy Survey. This galaxy exhibits complex morphological features, including a distinctive ribbed tail, referred to as 'ribs,' and thin, faint filamentary structures known as 'tethers' that stretch between two bright patches far from the host.
Aim: This work aims to unravel the origin of such distinctive, intricate morphologies of relativistic jets by examining the role of dynamical instabilities, with a specific focus on "MysTail".
Methods: We performed 3D relativistic magnetohydrodynamic (RMHD) simulations of rotating jets, with a particular focus on dynamical instabilities. We have further utilized the hybrid Eulerian-Lagrangian framework of the PLUTO code and generated synthetic synchrotron emission and polarisation maps at a radio frequency of 1.285 GHz to compare with the observed signatures of "MysTail". We conducted two types of simulation runs: one involving continuous jet injection and another where the jet injection was temporarily stopped for a significant period ($\approx$ 1.3 Myrs) before being restarted.
Results: Our analysis based on simulations of a continuously injected jet suggests that current-driven instabilities, notably the $|m|=1$ mode, are crucial in generating ribs-like structures. In the case of restarted jet simulation, the rib-like structures were formed via kink instability and were relatively near the nozzle. In both of these cases, the jet dissipates its pre-existing magnetic energy through these instabilities, transitioning to a more kinetic energy-dominant state. The turbulent structures in the vicinity of the forward shock that result from this dissipation phase are found to be filamentary in nature and resemble the tethers as observed for the case of “MysTail". Our simulations suggest that "MysTail" is a single contiguous source in a phase of restarted AGN activity undergoing MHD instabilities (ribs) as it propagates and dissipates energy forming turbulent filaments (tethers).
