Detection of broad ultraviolet Fe II lines in the spectrum of NGC 1068.

Abstract

Ultraviolet observations of the nucleus ofo NGC 1068, obtained by the IUE over a period of 5 yr, are combined to give a high signal-to-noise spectrum of this source. The ultraviolet stellar continuum, obtained by comparison with ground-based data, is subtracted to show the nuclear nonstellar component. The resulting spectrum shows clearly the presence of strong broad Fe II emission bands similar to those observed in many broad-line objects. Broad profiles are also seen in other strong emission lines. These observations confirm the recent discovery of an optical Seyfert type 1 spectrum in NGC 1068 by Antonucci and Miller (1985). Some of the findings do not support the claim by Antonucci and Miller that the polarized fraction of the nuclear flux is wavelength independent. The nonstellar continuum is much flatter than deduced in previous investigations and not very different from that observed in many Seyfert 1 nuclei. It did not vary by more than 15 percent over the 5 yr period. It is suggested that a search for the broad ultraviolet Fe II lines may be the best way to look for a 'hidden Seyfert 1 nucleus' in other narrow-line objects.