Astronomy and Astrophysics – Astrophysics
Scientific paper
Nov 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981apj...250...55s&link_type=abstract
Astrophysical Journal, Part 1, vol. 250, Nov. 1, 1981, p. 55-65.
Astronomy and Astrophysics
Astrophysics
262
Active Galactic Nuclei, Emission Spectra, Forbidden Bands, Line Spectra, Seyfert Galaxies, Spectrophotometry, Interstellar Extinction, Luminosity, Red Shift, Spectrum Analysis, Tables (Data), Temperature Effects
Scientific paper
Spectrophotometric observations are presented for emission-line galaxies. When combined with previous Lick Observatory measurements, they are used to deduce criteria that allow the Seyfert 2 phenomena to be quantitatively isolated from the narrow-emission-line galaxies. These criteria are based on the finding that galaxies with forbidden line O III 5007 A/H-beta ratios lower than 3 have emission line widths that are usually considerably smaller than the widths in galaxies with forbidden line O III 5007 A/H-beta ratios greater than 3. In addition, large He II 4686 A/H-beta ratios are consistent with forbidden line O III 5007 A/H-beta ratios greater than 3. The physical conditions in the narrow-line regions of Seyfert 1 galaxies are compared with those in Seyfert 2 galaxies. Significant differences are found for the temperature-sensitive forbidden line O III ratio, and for the luminosity of Fe VII forbidden line 6087 A relative to the luminosity of the low-ionization forbidden lines.
Osterbrock Donald E.
Shuder J. M.
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