X-RAY, UV AND FIR EMISSION OF SEYFERT-GALAXIES

We have compiled multiwavelength data (in the radio, FIR, optical, UV and X-ray ranges) for a sample of 126 galaxies, including QSO, Seyfert 1, Seyfert 2 and galaxies dominated by star-forming processes. We hav e tested the implications of ''unified Seyfert models'', which assume that Seyfert 1 and 2 galaxies are intrinsically the same kind of objec ts, but seen at different angles. A dense obscuring torus around the n ucleus would originate the spectral differences actually observed. Fro m our data we conclude that the UV-soft X-ray emission can not be seen through the torus. On the other hand, the occultation/reflection pict ure underestimates significantly the UV luminosity. We propose a schem e in which the intensity of the non-thermal nuclear engine decreases f rom QSO to Sy 2 galaxies, while the relative contribution of star-form ing regions increases in the same direction. The relatively low soft X -ray emission in Sy 2 galaxies implies that their UV radiation should be dominated by starbursts, rather than by the nuclear engine.