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Session 78 - Seyfert Galaxies.
Display session, Friday, January 09
As many others, the two Seyfert 2 galaxies NGC 5929 and NGC 2110 display bright extranuclear regions of line emission which are spatially associated with radio jets or lobes. The nature of the excitation and ionization mechanisms of this line emitting gas (shocks induced by the propagation of the radio ejecta, photoionization by the nuclear radiation...) remain very uncertain. Recent modelings either of shock excitation (e.g. Dopita amp; Sutherland, 1995) or nuclear photoionization (e.g. Binette, Wilson amp; Storchi-Bergmann, 1996) have stressed the importance of using UV lines diagnostic in addition to the classical optical ones to distinguish between these two families of mechanisms. In this context, we present new off-nucleus HST/FOS spectra of the two Seyfert galaxies NGC 5929 and NGC 2110. These spectra, obtained with the 0.43" diameter FOS aperture, cover spectral domains ranging from the far-UV to the optical (G130H, G190H, G400H and G570H configurations). The derived dereddened optical and UV line ratios are examined in view of the output of photoionization and/or shock codes and used to probe the excitation mechanism of the extranuclear line emitting gas and its relationship with the neighbouring radio ejecta.
Program listing for Friday