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Observations of Seyfert Galaxies with the International Ultraviolet Explorer

Published online by Cambridge University Press:  30 March 2016

Marie-Hélène Ulrich
Marie-Hélène Ulrich*
Affiliation:
European Southern Observatory CERN, Geneva, Switzerland

Abstract

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The most important observations of Seyfert nuclei to be done in the ultraviolet are 1) the determination of the non-stellar continuum energy distribution and 2) the measurements of the intensities of the permitted lines. The main results obtained so far with IUE on these two points are as follows.

The Lyman/Balmer intensity ratio is smaller than predicted by the recombination theory. It cannot be forced into agreement with recombination theory by applying the reddening correction relevant to the narrow line region nor to the continuum. This Lyman/Balmer ratio is therefore caused by the particular physical conditions prevailing in the broad-line region. The smallness of the Lyman/Balmer ratio and the non-detection of the resonance lines of Fell neither in emission nor in absorption show that collisional processes play a dominant role in the excitation of the lines in the broad-line region and that the density in this region is at least 3 × 1010 cm-3.

Type
Ultraviolet Astronomy-New Results from Recent Space Experiments
Information
Highlights of Astronomy , Volume 5: Highlights of Astronomy. As presented at the XVIIth General Assembly of the IAU, 1979 , 1980 , pp. 317 - 323
Copyright
Copyright © Cambridge University Press 1980

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