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Some Implications of Ultraviolet Observations of Quasars and Active Galaxies

Published online by Cambridge University Press:  14 August 2015

Arthur F. Davidsen
Arthur F. Davidsen*
Affiliation:
Department of Physics, The Johns Hopkins University, Baltimore, Maryland 21218, U.S.A.

Abstract

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The problem of the order of magnitude discrepancy in the expected and observed ratios of the Lyman and Balmer lines in quasars and active galaxies is reviewed. Whereas early photoionization models for the emission line regions predicted F(Lα)/F(Hβ) ≳ 40, the observations give values for this ratio in the range 3–8. Attempts at explaining the observations have involved dust, both external and internal to the emission line regions, and improved treatments of the collisional processes and radiative transfer effects in dense (Ne ~ 1010 cm−3), optically thick clouds. None of the effects considered is, by itself, able to explain all the observations, and a combination of several of them is probably required.

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 92: Objects of High Redshift , 1980 , pp. 235 - 245
Copyright
Copyright © Reidel 1980 

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