Magnetic confinement, magnetohydrodynamic waves and smooth line profiles in active galactic nuclei |
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Authors: | M. C. Bottorff Gary J. Ferland |
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Affiliation: | Department of Physics &Astronomy, University of Kentucky, Lexington, KY 40506-0055, USA |
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Abstract: | In this paper, we show that if the broad-line region clouds are in approximate energy equipartition between the magnetic field and gravity, as hypothesized by Rees, there will be a significant effect on the shape and smoothness of broad emission-line profiles in active galactic nuclei. Linewidths of contributing clouds or flow elements are much wider than their thermal widths, because of the presence of non-dissipative magnetohydrodynamic waves and their collective contribution produce emission-line profiles broader and smoother than would be expected if a magnetic field were not present. As an illustration, a simple model of isotropically emitting clouds, normally distributed in velocity, is used to show that smoothness can be achieved for less than ∼8×104 clouds and may even be as low as a few hundred. We conclude that magnetic confinement has far-reaching consequences for observing and modelling active galactic nuclei. |
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Keywords: | line: profiles magnetic fields MHD galaxies: active galaxies: nuclei |
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