Emission knots and polarization swings of swinging jets

TL;DR

This paper presents a model explaining the complex motion, brightness, and polarization behavior of emission knots in active galactic nuclei jets, accounting for observed non-ballistic dynamics and polarization swings.

Contribution

The model uniquely reproduces a wide range of observed knot behaviors, including non-ballistic motion, brightness variability, and polarization angle swings, in jets with helical magnetic fields.

Findings

Reproduces non-ballistic knot trajectories and oscillations.

Explains polarization angle swings and flux variability.

Accounts for random polarization jumps.

Abstract

Knots (emission features in jets of active galactic nuclei) often show non-ballistic dynamics and variable emission/polarization properties. We model these features as emission pattern propagating in a jet that carries helical magnetic field and is launched along a changing direction. The model can reproduce a wide range of phenomena observed in the motion of knots: non-ballistic motion (both smooth and occasional sudden change of direction, and/or oscillatory behavior), variable brightness, confinement of knots' motion within an overlaying envelope. The model also reproduces smooth large polarization angle swings, and at the same time allows for the seemingly random behavior of synchrotron fluxes, polarization fraction and occasional $\pi/2$ polarization jumps.