VSOP imaging of S5 0836+710: a close-up on plasma instabilities in the jet

The luminous high-redshift (z = 2.17) quasar S5 0836+710 has been observed at 5 GHz with the VSOP. We compare the properties of three images obtained from the observation: a low-resolution ground array image (dynamic range 46 00:1), a full-resolution VSOP image (900:1), and an image made with only th e space baselines (200:1). The space baselines alone are sufficient for a r eliable recovery of the source structure, within the limits of the achieved spatial sampling of the visibility data. The curved jet ridge line observe d in the images can be described by Kelvin-Helmholtz instabilities developi ng in a relativistic outflow with the Mach number of about 6. This descript ion holds on the scales of less than or similar to 700 h(-1)pc, and is show n to be consistent with variable apparent speeds observed in the jet.