Bending of radio jets in merging galaxy clusters: insights from MHD simulations

Abstract

Active Galactic Nuclei (AGNs) host powerful relativistic jets from their central engine. These jets interact with the surrounding stellar, galactic, or cluster mediums (ICM), producing several morphological features, which are also associated with feedback on the medium itself. Particularly in merging galaxy clusters, the radio jets from AGNs have been found to bend sharply, resulting in peculiar morphologies. These features, which were previously explained via wind-jet interaction models, have now been challenged since the discovery of a double scythe-shaped jet from MRC 0600-399 in the cluster Abell 3376. It has been reported to interact with magnetic fields draped around the cold front, which are regions of temperature and density discontinuity. Studying these interactions and resulting dynamical features has important implications for understanding the impact of AGNs on their surrounding environments and the nature of cold fronts in merging clusters. Using 3D MHD simulation through PLUTO, we have replicated this bending by emanating a supersonic outflow in a static ambient medium, which collides with a magnetised arch structure and produces sharply bent jets. In this thesis, we showcase the comparison between the simulation of the bending of jets in their interaction with such structures and the observed object MRC 0600-399. We find that the dynamical nature of bending is attributed to the magnetic tension directed towards the jet on stretching. As a result, Kelvin-Helmholtz instability (KHI) is inhibited in the upstream zone but not the downstream zone, where the tension is directed away from the jet. Following the dynamical evolution, we also adopted a hybrid Eulerian and Lagrangian framework in PLUTO which is used to understand the non-thermal emissions. We utilize this to produce a synthetic intensity map of synchrotron radio emissions for four different frequencies - 150 MHz, 310 MHz, 625 MHz and 1.28 GHz - and also plot spectral index maps using these frequencies. These synthetic observational signatures have then been compared with the observational datasets from MeerKAT.