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The Variable HI Absorption (z=0.524) in the Spectrum of AO 0235+164

Published online by Cambridge University Press:  04 August 2017

F. H. Briggs
F. H. Briggs*
Affiliation:
University of Pittsburgh

Extract

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The spectrum of AO 0235+164 (z>0.85) reveals the presence of absorbing gas (z=0.524) which has been studied extensively at radio and optical wavelengths (See Wolfe, Davis and Briggs, 1982 for bibliography). A program by Wolfe et al. to monitor the radio absorption line at 932 MHz showed that the profile had changed during a 5 year period. The observation led to a tightly constrained model in which variations in the source continuum were capable of driving the HI hyperfine level populations (and hence the optical depths of the features in the absorption line) by virtue of the hypothesized close proximity of the source to the clouds. A continued monitoring program has not shown the predicted correspondence between the continuum variation and the behavior of the individual features, and this model has therefore been ruled out.

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 110: VLBI and Compact Radio Sources , 1984 , pp. 49 - 50
Copyright
Copyright © Reidel 1984 

References

Briggs, F. H., 1983, Ap. J., in press.Google Scholar
Johnston, K. J., Broderick, J. J., Condon, J. J., Wolfe, A. M., Weiber, K., Genzel, R., Witzel, A., Booth, R. 1979, Ap. J., 234, 466.Google Scholar
Wolfe, A. M., Davis, M. M., Briggs, F. H. 1982, Ap. J., 259, 495.CrossRefGoogle Scholar
Wolfe, A. M., Broderick, J. J. Condon, J. J., and Johnston, K. J. 1978, Ap. J., 222, 752.Google Scholar