Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 1978
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978apj...221..486f&link_type=abstract
Astrophysical Journal, Part 1, vol. 221, Apr. 15, 1978, p. 486-500.
Astronomy and Astrophysics
Astrophysics
51
Astronomical Photometry, Astronomical Spectroscopy, Emission Spectra, Galactic Radiation, Helium Atoms, Seyfert Galaxies, Abundance, Atomic Spectra, Line Spectra, Quasars
Scientific paper
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.
Feldman F. R.
MacAlpine Gordon M.
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