Magnetohydrodynamic disc winds and linewidth distributions

Abstract

We study active galactic nucleus (AGN) emission-line profiles combining an improved version of the accretion disc wind model of Murray & Chiang with the magnetohydrodynamic (MHD) model of Emmering et al. We show how the shape, broadening and shift of the C IV line depend not only on the viewing angle to the object, but also on the wind launching angle, especially for small launching angles. We have compared the dispersions in our model C IV linewidth distributions to observational upper limit on that dispersion, considering both smooth and clumpy torus models. As the torus half-opening angle (measured from the polar axis) increases above about 18{ring operator}, increasingly larger wind launching angles are required to match the observational constraints. Above a half-opening angle of about 47{ring operator}, no wind launching angle (within themaximum allowed by theMHDsolutions) can match the observations. Considering a model that replaces the torus by a warped disc yields the same constraints as obtained with the two other models. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.