Seyfert galaxies and the radio - far-infrared correlation

We have observed a sample of 149 Seyfert galaxies and radio-quiet quasars a t 13 cm with both a 275-km radio interferometer and the 6-km compact array of the Australia Telescope. The high-resolution observations searched for t he presence of compact, high-brightness-temperature radio emission from the active nucleus. The low-resolution observations measured the total radio e mission from the galaxy disc and Seyfert core and lobes. From these we draw the following conclusions. (i) Seyfert galaxies that lack compact radio co res display a correlation between radio and far-infrared (FIR) emission sim ilar to the correlation displayed by normal spirals, albeit with greater sc atter. The correlation is found to be intrinsic and is not an artefact of t he richness effect. (ii) A very different radio-FIR correlation is displaye d by those Seyferts that harbour compact radio cores. These tend to be more radio-loud than either normal spirals or the Seyferts that lack compact co res. The compact core emission thus seems to be responsible for the general ly poor radio-FIR correlation displayed by Seyfert galaxies. (iii) The radi o-FIR correlation is not significantly improved by subtracting off the 0.1- arcsec (20- to 200-pc) compact radio emission from the total radio emission . This suggests that the emission from the active galactic nucleus has sign ificant structure on scales larger than 0.1 arcsec. Perhaps these structure s are the 'linear' radio features that have been seen previously in Seyfert nuclei.