VLBI OBSERVATIONS OF THE NUCLEAR JET IN CYGNUS-A

We present an image of the "core" and inner jet of Cygnus A at an angular resolution of 2 mas obtained from Mark III VLBI observations at 6 cm wavelength with an array of nine antennas. The core is resolved, at least partly due to its being broadened by scattering in the Galactic interstellar medium. The jet has several condensations out to a distance of approximately 25 mas from the core and has a fairly constant FWHM of approximately 2.2 mas. The parsec-scale jet points toward the arcsec-scale jet observed with the VLA to within 4-degrees. The ratio between the flux density of the jet and that of the counterjet is > 15:1. From a comparison with an earlier VLBI image of Cygnus A, we find an upper limit to the apparent velocity of the brightest knot in the jet of about 2c, where c is the speed of light (for H0 = 60 km s-1 Mpc-1,q0 = 0).