On the large scale morphology of Hercules A: destabilized hot jets?

ABSTRACT Extragalactic jets are generated as bipolar outflows at the nuclei of active galaxies. Depending on their morphology, they classified Fanaroff–Riley type I (FRI) (centre-brightened) and II (FRII) (edge-brightened) radio jets. However, this division is not sharp, observations these sources large scales often show intermediate jet morphologies or even hybrid with a FRI one side FRII other. A good example galaxy that difficult to classify Hercules A. This source shows bright lobes (a common feature jets) albeit without hotspots indicative violent interaction between ambient medium impact region, because seem be disrupted inside distance from bow shocks surrounding lobes. In paper, we explore physics could trigger peculiar morphology by means three-dimensional relativisitic hydrodynamical simulations. Our results large-scale morphological features can reproduced propagation relativistically hot plasma outflow helical instability modes, generates lobe expands isotropically against pressure-decreasing intergalactic medium. We also discuss implications result may have for host nucleus in terms possible transition high-excitation low-excitation modes.