The jet and filaments in Cygnus A.

Multiconfiguration VLA observations of Cygnus A at 1.4 and 5 GHz have been used to produce detailed maps of exceptional dynamic range. A radio jet extends from the core into the northwest lobe. The broad radio lobes reveal an unexpected wealth of filamentary structure. Two new hot spots are identified. The pressure of the cluster gas in which Cyg A is embedded appears to be insufficient to confine either the jet or the filaments. From the necessarily high mechanical luminosity of the jet and the high energy densities of the hot spots, it is concluded that the jet is probably relativistic. The surface brightness of the jet is high in absolute terms, but the total radiated power of the jet is only 0.001 of that of the whole source.