ISSN:
1572-946X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract 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 have tested the implications of “unified Seyfert models”, which assume that Seyfert 1 and 2 galaxies are intrinsically the same kind of objects, but seen at different angles. A dense obscuring torus around the nuclcus would originate the spectral differences actually observed. From 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 picture underestimates significantly the UV luminosity. We propose a scheme in which the intensity of the non-thermal nuclear engine decreases from QSO to Sy 2 galaxies, while the relative contribution of star-forming 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00657965
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