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

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.