Open AccessMagnetic confinement, magnetohydrodynamic waves and smooth line profiles in active galactic nuclei
Author(s) -
Bottorff M. C.,
Ferland Gary J.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03465.x
Subject(s) - physics , astrophysics , magnetohydrodynamic drive , magnetohydrodynamics , active galactic nucleus , magnetic field , line (geometry) , equipartition theorem , field line , accretion (finance) , dissipative system , computational physics , galaxy , geometry , mathematics , quantum mechanics
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 ∼8×10 4 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.