The extended narrow line region of NGC 4151. I. Emission line ratios and their implications

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The paper presents the first results from long-slit spectra of the Seyfert galaxy NGC 4151 which give average diagnostic ratios of weak lines in the extended narrow line region (ENLR) of that galaxy and the first direct density measurement in an ENLR. These data confirm that the ENLR is kinematically undisturbed gas in the disc of the galaxy which is illuminated by an ionizing continuum stronger by a factor of 13 than a power law interpolated between observed ultraviolet and X-ray fluxes. Explanations of this apparent excess include a hot thermal continuum, time variations and an anisotropic radiation field. The authors give reasons for favouring anisotropy which might be caused by shadowing by a thick accretion disc or by relativistic beaming. Shadowing by a molecular torus is unlikely, given the absence of an infrared signal from the reradiated flux absorbed by any torus. Anisotropy would have important implications for the bolometric luminosity and nature of active galactic nuclei

NATURVETENSKAP Fysik Astronomi, astrofysik och kosmologi hsv//swe
NATURAL SCIENCES Physical Sciences Astronomy, Astrophysics and Cosmology hsv//eng
Experimental/ astronomical spectra
galactic nuclei
interstellar matter
Seyfert galaxies
visible astronomical observations/ AD 1989 05 05 to 06
interstellar medium
extended narrow line region
NGC 4151
spectra
Seyfert galaxy
density
kinematically undisturbed gas
hot thermal continuum
time variations
anisotropic radiation field
shadowing
thick accretion disc
relativistic beaming
bolometric luminosity
active galactic nuclei
315 to 695 nm/ A9850R Active and peculiar galaxies A9850E Galactic structure
content and morphology A9840B Interstellar matter A9580J Photographic region astronomical observations/ wavelength 3.15E-07 to 6.95E-07 m

Av författaren/redakt...: Penston, M. V.; Robinson, A.; Alloin, D.; Appenzeller, I.; Aretxaga, I.; Axon, D. J.; visa fler...; Baribaud, T.; Barthel, P.; Baum, S. A.; Boisson, C.; de Bruyn, A. G.; Clavel, J.; Colina, L.; Dennefeld, M.; Diaz, A.; Dietrich, M.; Durret, F.; Dyson, J. E.; Gondhalekar, P.; van Groningen, E ...; Jablonka, P.; Jackson, N.; Kollatschny, W.; Laurikainen, E.; Lawrence, A.; Masegosa, J.; McHardy, I.; Meurs, E. J. A.; Miley, G.; Moles, M.; O'Brien, P.; O'Dea, C.; del Olmo, A.; Pedlar, A.; Perea, J.; Perez, E.; Perez-Fournon, I ...; Perry, J.; Pilbratt, G.; Rees, M.; Robson, I.; Rodriguez-Pascua ...; Rodriguez Espino ...; Santos-Lleo, M.; Schilizzi, R.; Stasinska, G.; Stirpe, G. M.; Tadhunter, C.; Terlevich, E.; Terlevich, R.; Unger, S.; Vila-Vilaro, V.; Vilchez, J.; Wagner, S. J.; Ward, M. J.; Yates, G. J.; visa färre...

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