EVN and MERLIN observations of five superluminal radio sources.

An attempt is made to fill the resolution gap between the milliarcsecond (mas) and arcsecond scales of previous observations of superluminal sources. Observations of five sources (NRA0140, 3C120, 3C179, 3C279, and 3C345) were made with the European VLBI Network (EVN) at 1.66 and 5 GHz and MERLIN observations at 5 GHz. Hybrid maps constructed from these observations show that - except mainly for 3C120 neither the EVN nor the MERLIN maps show very much extended emission outside the respective cores. An analysis of the instrumental limitations shows that the lack of extended emission is not due to insufficient UV coverage. The quality of the maps, in fact, is comparable to or (in the case of MERLIN) better than that of the higher resolution maps showing the actual superluminal motion. The conclusion is that on the angular scales of the present observations the intensity of the jet emission is lower than on smaller angular scales while on much larger angular scales, local features of higher brightness occur.