Seyfert galaxies with weak broad H alpha emission lines
Abstract
Spectrophotometric measurements show five galaxies with strong narrow emission lines combined with weak, broad H-alpha and H-beta components to have line and continuum spectral properties intermediate between those of Seyfert 1 and Seyfert 2 galaxies. Because they are closer to the latter, they are called Seyfert 1.8 and Seyfert 1.9, depending on the presence of broad H-beta emissions in the scans. The observed intensity ratios of the broad H-alpha/H-beta emission lines are large compared with those of typical Seyfert 1 galaxies, suggesting the importance of dust in the broad-line regions. Narrow-line spectra of the Seyfert 1.8 and 1.9 are found to have low ionization, implying that their narrow-line region is reached by few high-energy photons. Emphasis is placed on the correlation between a strong, featureless continuum and broad H I emission lines in Seyfert and radio galaxies.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1981
- DOI:
- 10.1086/159306
- Bibcode:
- 1981ApJ...249..462O
- Keywords:
-
- Emission Spectra;
- H Alpha Line;
- H Beta Line;
- Seyfert Galaxies;
- Spectrophotometry;
- Astronomical Photometry;
- Forbidden Bands;
- Ionization;
- Radio Galaxies;
- Spectrum Analysis;
- Tables (Data);
- Astronomy