An extended nebulosity of highly ionized gas in the SB0 Seyfert galaxy NGC 3516 : detection and study of the physical conditions of the gas.
Abstract
Spectrographic and spectrophotometric observations of a nebulosity of ionized gas surrounding the nucleus of the Seyfert galaxy NGC 3516 are presented. Photoionization models have been calculated for this bright cloud in which the ionizing source is the central nonthermal source. Charge-transfer reactions of several ions with H(0) and, in particular, a charge-transfer rate coefficient for O(plus plus) of 8 x 10 to the -10th cu cm/s are included in the models. Good agreement with the observations is obtained, using a model where the cloud is nearly optically thick and has a uniform density of about 30 per cu cm, i.e., a density definitely smaller than the electron density of about 1000 per cu cm in the narrow-line region in the nucleus. The abundances of the extranuclear gas are nearly normal. The total mass of the nebulosity is at least 10 million solar masses. The photoionization models are valid for any nebulosity illuminated by a power-law spectrum and where the collisional de-excitation can be neglected (uniform density less than 1000 per cu cm). The data are consistent with possible origins that are presented for the extended gaseous nebulosity
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1980
- DOI:
- 10.1086/157956
- Bibcode:
- 1980ApJ...238...45U
- Keywords:
-
- Galactic Nuclei;
- Ionized Gases;
- Nebulae;
- Seyfert Galaxies;
- Astronomical Models;
- Astronomical Spectroscopy;
- Emission Spectra;
- Line Spectra;
- Photoionization;
- Astrophysics