Compact Radio Components in Seyfert Nuclei

Although initial, low resolution radio measurements by deBruyn and Wilson (1978), suggested that the radio emission in Seyfert nuclei was in approximate pressure equilibrium with thermal gas in the Narrow Line Region (NLR), higher resolution radio measurements using the VLA and MERLIN (eg Unger et al. 1985) showed that the radio components were at significantly higher pressures than the NLR thermal gas. This is even more apparent in the very long baseline interferometry (VLBI) observations using the European Network (EVN). Observations of NGC4151 (Harrison et al.1986) and NGC7674 (Unger et al. 1988) have already been described, together with a summary of work in progress by Pedlar et al. 1987. Several Seyfert nuclei have components in which relativistic particle/magnetic field pressures as high as 10−7 dynes/cm2 are infered. These observations are also consistent with the collimated ejection of either radio emitting ‘plasmons’ or beams from the optical nucleus.