FAINT OBJECT SPECTROGRAPH OBSERVATIONS OF THE LOW-LUMINOSITY SEYFERT-GALAXY NGC-1566

FOS observations of the Seyfert galaxy NGC 1566 show it to possess the broad lines characteristic of a typical Seyfert 1 galaxy, even in states of very low luminosity. The continuum, however, is steep (f-nu approximately nu-1.5) with no suggestion of the ultraviolet excess seen in higher luminosity AGNs. The broad emission lines have symmetric profiles, but are redshifted by 200-1000 km s-1 relative to the systemic velocity. The broad-line ratios indicate a low ionization parameter, and the strength of lines such as Fe II, Mg II, and the Balmer continuum relative to the UV continuum supports models for X-ray heating of the broad-line cloud interiors. The sharp core of the HST point response function gives a significant advantage over ground-based telescopes for observations of low luminosity active galaxies, despite the spherical aberration of the primary mirror. The high contrast of the active nucleus over the surrounding starlight permits observers to use the small apertures of the FOS to reject most of the contaminating starlight that frustrates ground-based observations and to obtain nearly simultaneous spectra spanning the full UV and optical wavelength range.