A theoretical and observational analysis of He I triplet lines in class 1 Seyfert galaxy spectra.
Abstract
The equations of statistical equilibrium are solved for 11 levels of the helium atom that are most relevant to the production and radiative transfer of He I triplet lines. Solutions are obtained for several densities and temperatures over a run of optical depth in the 10,830-A line, and the results for emission-line strengths are plotted. Spectrophotometric scans and pertinent line strengths are presented for the class 1 Seyfert galaxies 3C 120, NGC 7469, and Mrk 618, as well as for Mrk 335, which exhibits a 'more normal' He I 5876/H-beta ratio. A comparison of the theoretically determined line intensities with the observational results verifies that the He I triplet line intensities are significantly enhanced by electron collisional excitation from 2(3)P and 2(3)S. It is suggested that the gas which gives rise to the broad He I lines in 3C 120, Mrk 618, and NGC 7469 is characterized by a number density of about 5 billion per cu cm, a temperature of approximately 15,000 K, and an optical depth of 100 to 120 in the 10,830-A line.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1978
- DOI:
- 10.1086/156050
- Bibcode:
- 1978ApJ...221..486F
- Keywords:
-
- Astronomical Photometry;
- Astronomical Spectroscopy;
- Emission Spectra;
- Galactic Radiation;
- Helium Atoms;
- Seyfert Galaxies;
- Abundance;
- Atomic Spectra;
- Line Spectra;
- Quasars;
- Astrophysics;
- Helium:Seyfert Galaxies;
- Seyfert Galaxies:Spectra