MERLIN and VLBI observations of the quasar 0836+710 : morphology of a parsec-kiloparsec scale jet.

The quasar 0836+710 (4C 71.07, z = 2.16, S_1.7 GHz_ = 3.6 Jy) was observed at 1.7 GHz for 19 h simultaneously with a 16-station VLBI array and the 7-station MERLIN array. The bright and pronounced one-sided jet emerging from the core, which has been reported by Krichbaum et al. A&A 230, 271 (1990) to contain stationary and superluminally moving components, has been mapped with 3 milliarcsecond (mas) resolution over its total visible length of 130 mas at a dynamic range of 1000 to 1. On these scales, the jet displays smooth bending, as well as a regular kink pattern, possibly due to magneto-hydrodynamic instabilities. On larger scales, 0836+710 displays a diffuse secondary component aligned with the jet component located 1.3 arcseconds from the core. However, no emission could be found between the pc-scale structure and the diffuse component at a level of l mJy per beam, with a beam of 0.22 arcseconds. The secondary component has been mapped with 50 mas resolution using the combined VLBI and MERLIN data. The emission appears to be very diffuse, displaying no dominant hot spot. Here the jet pressure may have declined to match the ambient pressure, thus leading to a loss of confinement of the jet and the subsequent formation of diffuse emission.