MULTIWAVELENGTH ANALYSIS OF QUASARS, SEYFERT-GALAXIES, AND STARBURSTS

We have analyzed the multiwavelength (radio to X-ray) properties of a sample of nearly 100 galaxies with different levels of activity: quasi -stellar objects, Seyfert 1 and 2 galaxies, and starburst galaxies. We have tested the implications of ''unified Seyfert models,'' which ass ume that Seyfert 1 and 2 galaxies are intrinsically similar but seen a t different angles through a dense obscuring torus. We have found sign ificant differences between the continuum energy distribution of both Seyfert classes at high energies, with a systematic lack of UV and X-r ay (soft and hard) emission in Seyfert 2 compared to Seyfert 1 galaxie s. The measured ratios between the emission at various wavelengths dif fer from the values predicted by the ''occultation/reflection'' pictur e. It is necessary to complement this picture with additional energy s ources to reconcile it with the observational results. We discuss brie fly in this contribution the nature of these sources.