Kelvin-Helmholtz modes revealed by the transversal structure of the jet in 0836+710

TL;DR

This study uses high-resolution space VLBI observations to identify Kelvin-Helmholtz instability modes in the jet of quasar 0836+710, revealing stratification and mode growth at different radii, which informs jet physics.

Contribution

First direct identification of Kelvin-Helmholtz modes in an extragalactic jet using space VLBI data, linking observed structures to jet stratification and instability growth.

Findings

Kelvin-Helmholtz instability causes observed jet oscillations.

Jet stratification influences mode growth at different radii.

Driving frequency impacts active nucleus physics.

Abstract

Studying transversal structure in extragalactic jets is crucial for understanding their physics. The Japanese led space VLBI project VSOP has offered arguably the best opportunity for such studies, by reaching baseline lengths of up to 36,000 km and resolving structures down to an angular size of 0.3 mas at 5 GHz. VSOP observations of the jet in 0836+710 at 1.6 and 5 GHz have enabled tracing the radial structure of the flow on scales from 2 mas to 200 mas and determining the wavelengths of individual oscillatory modes responsible for the formation of the structure observed. We conclude that these modes are produced by Kelvin-Helmholtz instability in a sheared relativistic flow. Our results point towards the stratification of the jet and the growth of different modes at different jet radii. We also discuss the implications of the driving frequency on the physics of the active nucleus of the quasar.