The extended narrow-line region in radio Seyferts: evidence for a collimated nuclear UV field?
Open Access
- 1 October 1987
- journal article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 228 (3) , 671-679
- https://doi.org/10.1093/mnras/228.3.671
Abstract
Long-slit spectra of seven Seyfert galaxies reveal high-excitation ([O III] λ5007/Hβ≈5) emission-line gas up to 20 kpc from the galactic nuclei. The low velocity dispersion (FWHM−1) and orderly velocity field, characteristic of normal galactic rotation, suggest that this emission-line region, the Extended Narrow Line Region (ENLR), is physically distinct from the classical Narrow Line Region (NLR). The large physical extent, high excitation and kinematic properties of the ENLR point to it being ambient gas in the disc or halo of the galaxy which is photoionized by the nuclear radiation field. Despite the disparity in their physical sizes, the ENLR is substantially more extended parallel to the axis of the NLR radio structure than perpendicular to it. We argue that this elongation is due to an anisotropy in the nuclear radiation field whose origin is intimately related to the collimation of the radio ejecta.Keywords
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