NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-25 T02:21:32 PDT
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For refcode 2003MNRAS.343..192R:
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NED Abstract

Copyright by Royal Astronomical Society. 2003MNRAS.343..192R Near-infrared spectroscopy of nearby Seyfert galaxies - II. Molecular content and coronal emission Reunanen, J.; Kotilainen, J. K.; Prieto, M. A. Abstract. We present subarcsec near-infrared 1.5-2.5 microns moderate resolution long-slit spectra of eight nearby Seyfert galaxies (z < 0.01), both parallel to the ionization cone and perpendicular to it. These spectra complement similar data on six Seyferts, presented in Reunanen, Kotilainen & Prieto, and are used to study the spatial extent of the line emission, the integrated masses of excited H_2_ and the excitation mechanisms of interstellar gas. Large concentrations of molecular gas (H_2_) are present in the nucleus regardless of the Seyfert type. The spatial extent of the H_2_ emission is larger perpendicular to the cone than parallel to it in 6/8 (75 per cent) galaxies, in agreement with the unified models of active galactic nuclei. The full width at half maximum (FWHM) sizes of the nuclear H_2_ emission range from <20 to ~300 pc, and are larger than the predicted sizes for molecular torus (1-100 pc). Thus the emission probably arises from the material surrounding the torus rather than directly from the torus. Broad Br{gamma} was detected in nearly half of the optically classified Seyfert 2 galaxies, including two objects with no evidence for a hidden polarized broad line region. This high detection rate stresses the importance of extinction effects as the main cause for the Seyfert dichotomy. Br{gamma} and [Fe II] correlate both spatially and kinematically. Nuclear [Fe II] emission is generally blueshifted which, together with the high Br{gamma}/[Fe II] ratios, suggests shocks as the dominant excitation mechanism in Seyfert galaxies. Bright coronal emission lines [SiVI] and [Si VII] are common in Seyferts, as they are detected in ~60 per cent of the galaxies. In three galaxies the coronal lines are extended only in the direction parallel to the cone. This could be explained by a strongly collimated radiation field or, most plausibly, by shock excitation due to the jet or superwind interacting with the interstellar medium. Keywords: galaxies: active, galaxies: nuclei, galaxies: Seyfert, infrared: galaxies
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