NASA/IPAC EXTRAGALACTIC DATABASE
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For refcode 1998AJ....115..460M:
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1998AJ....115..460M HIGH-IONIZATION NUCLEAR EMISSION-LINE REGION IN THE SEYFERT GALAXY TOLOLO 0109-383 TAKASHI MURAYAMA AND YOSHIAKI TANIGUCHI Astronomical Institute, Tohoku University, Aoba, Sendai 980-77, Japan; murayama@astroa.astr.tohoku.ac.jp, tani@astroa.astr.tohoku.ac.jp AND KAZUSHI IWASAWA Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, England, UK; ki@ast.cam.ac.uk Received 1997 July 31; revised 1997 October 20 ABSTRACT We present a detailed optical spectroscopic analysis of the high- ionization Seyfert galaxy Tololo 0109-383, which was classified originally as a type 2 Seyfert nucleus. The high-ionization nuclear emission-line region (HINER) (traced by e.g., [Fe X] {lambda}6374) of this galaxy is found to be spatially extended. Although the total radial extent of the HINER amounts to ~1.1 kpc, ~70% of the HINER emission is concentrated in the inner 220 pc in radius. The inner HINER in Tololo 0109-383 can be interpreted by the photoionization model of Ferguson, Korista, & Ferland, while the extended HINER suggests that low-density interstellar medium is also photoionized by high-energy continuum emission as described by Korista & Ferland. We find an extended low-ionization emission line region traced by H{alpha}, [N II], and [S II] emission lines with very narrow widths (<200 km s^-1^) at ~2.2 kpc east of the nucleus. This region is characterized by (1) the observed [N II]/H{alpha} ratio, which is ~0.8; (2) no measurable [O III] emission; and (3) a low ionization parameter, U ~ 6 x 10^-5^. These properties can also be interpreted in terms of a photoionization model. As well as confirmation of the presence of broad emission in both H {alpha} and H{beta} lines, we also find optical Fe II emission features in our spectra. Since the optical Fe II emission is one of the important characteristics of type 1 active galactic nuclei, it is shown that Tololo 0109-383 harbors a type 1 central engine in its nucleus. Since the soft X-ray-to-infrared (60 [μ]m) luminosity ratio of Tololo 0109-383 is higher than those of typical type 2 Seyfert nuclei, we consider that blocking by a dusty torus may be incomplete and thus we are able to observe the type 1 nature of Tololo 0109-383. Key words: galaxies: nuclei-galaxies: Seyfert
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