NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-22 T11:38:33 PDT
Help | Comment | NED Home

For refcode 2000AJ....119.2605N:
Retrieve 124 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
2000AJ....119.2605N HIGH-IONIZATION NUCLEAR EMISSION-LINE REGION OF SEYFERT GALAXIES TOHRU NAGAO, YOSHIAKI TANIGUCHI, AND TAKASHI MURAYAMA Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai 980-8578, Japan Received 1999 December 28; accepted 2000 March 3 ABSTRACT Recently, Murayama & Taniguchi proposed that a significant part of the high-ionization nuclear emission-line region (HINER) in Seyfert nuclei arises from the inner wall of dusty tori because type 1 Seyfert nuclei (S1s) show excess HINER emission with respect to type 2 Seyfert nuclei (S2s). This means that the radiation from the HINER is anisotropic, and thus statistical properties of the HINER emission can be used to investigate the viewing angle toward dusty tori for various types of Seyfert nuclei. In order to investigate viewing angles toward narrow-line Seyfert 1 galaxies (NLS1s) and intermediate types of Seyfert galaxies (i.e., type 1.5, 1.8, and 1.9 Seyfert galaxies, hereafter S1.5, S1.8, and S1.9, respectively), we apply this HINER test to them. We also apply the same test for S2s with and without the hidden broad-line region. The sample of Seyfert nuclei analyzed here consists of 124 Seyfert nuclei compiled from the literature. Our main results and suggestions are as follows: (1) The NLS1s are viewed more face-on toward dusty tori than the S2s. However, the HINER properties of the NLS1s are indistinguishable from those of the S1s. (2) The S1.5s appear to compose heterogeneous populations; e.g., (a) some of them may be seen from an intermediate viewing angle between S1s and S2s, (b) some S1.5s are basically S1s but a significant part of the broad- line region (BLR) emission is accidentally obscured by dense, clumpy gas clouds, or (c) some S1.5s are basically S2s, but a part of the BLR emission can be seen from some optically thin regions of the dusty torus. (3) The S1.8s, the S1.9s, and the objects showing either a broad Pa{beta} line or polarized broad Balmer lines are seen from a large inclination angle, and the emission from the BLRs of such objects reaches us through optically thin parts of dusty tori. These three results support strongly the current unified model of Seyfert nuclei. Finally, (4) the line ratios of [Fe X] {lambda}6374 to the low-ionization emission lines are rather more isotropic than those of [Fe VII] {lambda}6087. Therefore, it is suggested that the [Fe X] {lambda}6374 emission is not useful for investigating the viewing angle toward the dusty torus in Seyfert nuclei. The most plausible reason seems to be that the [Fe X] {lambda}6374 emission is spatially extended, and thus its strength tends to show less viewing-angle dependence. Key words: galaxies: nuclei-galaxies: Seyfert-quasars: emission lines
Retrieve 124 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home