Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 1978
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978phys...17..285o&link_type=abstract
(Niels Bohr Institut, Teknisk Videnskabelige Forskningsrad, and Nordisk Institut for Teoretisk Atomfysik, Symposium on Quasars a
Astronomy and Astrophysics
Astrophysics
60
Emission Spectra, Galactic Nuclei, Ionized Gases, Radio Galaxies, Seyfert Galaxies, Abundance, Astronomical Models, Astrophysics, Cosmic Dust, Electron Density (Concentration), Electron Energy, Energy Transfer, Gas Ionization, Line Spectra
Scientific paper
The physical properties of the ionized gas in the active nuclei of Seyfert and radio galaxies derived from their emission-line spectra, are reviewed. Mean densities and temperatures in Seyfert 2 and narrow-line radio galaxies are in the ranges of less than 1000-10,000 per cu cm and 10,000-20,000 deg respectively, while in the narrow-line regions of Seyfert 1 and broadline radio galaxies the temperatures are similar but the densities range up to 1,000,000 per cu cm. In the broad-line regions the densities are 100,000,000 per cu cm or greater. The abundances of the elements seem more or less normal. The relative strengths of the lines approximately match photoionization models with a power-law input spectrum, including the presence of high-ionization with forbidden lines such as Fe X and Fe XI along with great strength of neutral and low-ionization forbidden lines such as O I, N I, and S II. The Fe II emission which occurs in most Seyfert 1 galaxies but is much weaker or absent in broad-line radio galaxies occurs in the broad-line high-density region.
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