1995A&A...293...44R

We present two high dynamic range images of the quasar 3C345 from observations at λ18cm (1990.74) and at λ49cm (1990.72). The simultaneous observations at two wavelengths have made it possible to construct a spectral index map covering the core and the extended jet. At a distance of ∼15mas the jet flares out and the emission beyond this is probably due to optically thick self-absorbed synchrotron radiation, while the radiation downstream is due to emission from an adiabatically expanding plasma. We conclude that the flaring out is either due to a standing shock caused by the jet passing into a region of different density, or due to large scale oscillations in a helical jet disrupting the collimated flow. There is a tentative detection of a feature extending perpendicular from the jet in connection with the jet flaring out. We suggest that this either may be the beamed part of a backflow connected to the standing shock and the turbulent region, or a coherent structural part of a wider turbulent flow.