Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981apj...251..465m&link_type=abstract
Astrophysical Journal, Part 1, vol. 251, Dec. 1981, p. 465-470.
Astronomy and Astrophysics
Astrophysics
43
Astronomical Spectroscopy, Helium, Line Spectra, Quasars, Seyfert Galaxies, Emission Spectra, Interstellar Extinction, Lyman Alpha Radiation, Spectral Line Width
Scientific paper
An assessment is given of the He II 4686 A/H-beta intensity ratio in class 1 Seyfert galaxies or quasars, which is used in the testing of calculations that attempt to explain Lyman line/Balmer line ratios through the collisional excitation of the Balmer lines without reddening. The model fails to produce sufficient emission for the 4686 A line under the assumption that it arises from recombination and relative cascading, and a comparison of observed and calculated equivalent widths suggests that the continua are altered by reddening. The only promising alternative 4686 A emission contributing process is the pumping of the He(+)(2-4) transition by hydrogen Lyman-alpha photons, although in this case the He 1640 A/4684 A ratio loses its validity as an observational test for reddening.
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