Astronomy and Astrophysics – Astrophysics
Scientific paper
1999-07-20
Astronomy and Astrophysics
Astrophysics
To appear in the Astronomical Journal. 13 pages, including 1 table and 4 figures. Uses emulateapj.sty
Scientific paper
10.1086/301055
The detection of polarized continuum and line emission from the nucleus of NGC 4258 by Wilkes et al. (1995) provides an intriguing application of the unified model of Seyfert nuclei to a galaxy in which there is known to be an edge-on, rotating disk of molecular gas surrounding the nucleus. Unlike most Seyfert nuclei, however, NGC 4258 has strongly polarized narrow emission lines. To further investigate the origin of the polarized emission, we have obtained spectropolarimetric observations of the NGC 4258 nucleus at the Keck-II telescope. The narrow-line polarizations range from 1.0% for [S II] 6716 to 13.9% for the [O II] 7319,7331 blend, and the position angle of polarization is oriented nearly parallel to the projected plane of the masing disk. A correlation between critical density and degree of polarization is detected for the forbidden lines, indicating that the polarized emission arises from relatively dense (n_e > 10^4 cm^-3) gas. An archival Hubble Space Telescope narrow-band [O III] image shows that the narrow-line region has a compact, nearly unresolved core, implying a FWHM size of <2.5 pc. We discuss the possibility that the polarized emission might arise from the accretion disk itself and become polarized by scattering within the disk atmosphere. A more likely scenario is an obscuring torus or strongly warped disk surrounding the inner portion of a narrow-line region which is strongly stratified in density. The compact size of the narrow-line region implies that the obscuring structure must be smaller than ~2.5 pc in diameter.
Antonucci Robert
Barth Aaron J.
Breugel Wil van
Brotherton Michael S.
Filippenko Alexei V.
No associations
LandOfFree
Polarized Narrow-Line Emission from the Nucleus of NGC 4258 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Polarized Narrow-Line Emission from the Nucleus of NGC 4258, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polarized Narrow-Line Emission from the Nucleus of NGC 4258 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-438833