The Spectral Energy Distribution of the Seyfert Galaxy Ton S180

We present spectral results from a multi-satellite, broad-band campaign onthe Narrow-line Seyfert 1 galaxy Ton S180 performed at the end of 1999. Wediscuss the spectral-energy distribution of the source, combining simultaneousChandra, ASCA and EUVE data with contemporaneous FUSE, HST, and ground-basedoptical and infra-red data. The resulting SED shows that most of the energy isemitted in the 10 -- 100 eV regime, which must be dominated by the primaryenergy source. No spectral turnover is evident in the UV regime. This, thestrong soft X-ray emission, and the overall shape of the SED indicate thatemission from the accretion disk peaks between 15 and 100 eV. High resolutionFUSE spectra showing UV absorption due to O VI and the lack of detectable X-rayabsorption in the Chandra spectrum demonstrate the presence of a low columndensity of highly ionized gas along our line-of-sight. The highly-ionized stateof the circumnuclear gas is most likely linked to the high luminosity and steepspectrum of the active nucleus. Given the strong ionizing flux in Ton S180, itis possible that the clouds within a few tens of light days of the centralsource are too highly ionized to produce much line emission. Thus the narrowwidth of the emission lines in Ton S180 is due to the emission arising fromlarge radii.Comment: 38 pages, 8 figures, some color figures. Accepted for publication in the Astrophysical Journa