The Trails of Superluminal Jet Components in 3C111

TL;DR

This paper analyzes superluminal jet components in 3C111 using VLBA observations, revealing jet dynamics, shock formation, and interactions with the environment during a major radio outburst, providing insights into AGN jet physics.

Contribution

It presents detailed VLBA monitoring of 3C111's jet during a major outburst, identifying shock structures and jet-environment interactions not previously observed in such detail.

Findings

Formation of leading and following jet components as shocks.

Jet expansion, acceleration, and recollimation in steep gradients.

Trailing components possibly caused by Kelvin-Helmholtz instability.

Abstract

In 1996, a major radio flux-density outburst occured in the broad-line radio galaxy 3C111. It was followed by a particularly bright plasma ejection associated with a superluminal jet component, which has shaped the parsec-scale structure of 3C111 for almost a decade. Here, we present results from 18 epochs of Very Long Baseline Array (VLBA) observations conducted since 1995 as part of the VLBA 2 cm Survey and MOJAVE monitoring programs. This major event allows us to study a variety of processes associated with outbursts of radio-loud AGN in much greater detail than has been possible in other cases: the primary perturbation gives rise to the formation of a leading and a following component, which are interpreted as a forward and a backward-shock. Both components evolve in characteristically different ways and allow us to draw conclusions about the work flow of jet-production events; the expansion, acceleration and recollimation of the ejected jet plasma in an environment with steep pressure and density gradients are revealed; trailing components are formed in the wake of the primary perturbation possibly as a result of coupling to Kelvin-Helmholtz instability pinching modes from the interaction of the jet with the external medium. The interaction of the jet with its ambient medium is further described by the linear-polarization signature of jet components traveling along the jet and passing a region of steep pressure/density gradients.