THE HOST GALAXIES OF NEARBY SEYFERT-1 NUCLEI

We use optical and infrared imaging data of a complete hard X-ray sele cted sample of AGN to investigate the host galaxies of nearby Seyfert 1 nuclei. We disentangle the emission due to the unresolved point sour ce and the resolved host galaxy by means of luminosity profile fitting . The stellar colours in the nucleus are redder in B-V and V-K than in normal spiral bulges or current stellar evolutionary models, probably due to dust obscuration. J-H colour is quite normal but H-K usually v ery red, probably indicating a large contribution from reradiating hot dust to the IR colours. No significant difference in IR colours oi th e stellar component is found with respect to a comparison sample of Li ners and starbursts, except that the reradiating dust in Seyferts tend s to be hotter and lie closer to the nucleus. B-V colour gets slightly bluer towards the nucleus, whereas V-A and J-K have red gradients. B- V and J-K gradients are not correlated and are likely to be caused by different mechanisms. There is a clear correlation between the AGN and host luminosity. Finally, we present optical colour ratio maps of two Seyfert nuclei, NGC 3227 and NGC 7469. The blue, ringlike or elongate d structure in the maps and its correspondence with molecular CO geome try is interpreted as evidence for circumnuclear star formation in the se AGN.