Search for Structural Changes in the Cores of “Nearby” Radio Galaxies

Abstract

Recent VLBI observations of the central radio components in the lobe-dominated radio galaxies 3C111 (Götz et al. 1987) and 3C390.3 (Alef et al. 1987) show drastic changes in the structure of the compact emission regions. In 3C111 a jet-like feature with two knots and a flux density of 600 mJy which was visible in 1980.4 had disappeared in 1985.4. This implies “superluminal behaviour” with a characteristic speed of ≳ 3c. In 3C390.3, there is also evidence for superluminal motion: radio knots appear to be ejected from the core at a rate of about one every 4 years and move out with an apparent velocity of 4.1 c (Ho = 50 km/s/Mpc throughout this paper) in the direction of the north-west extended lobe.