MHD Disc Winds and Linewidth Distributions

TL;DR

This paper combines advanced accretion disc-wind and magneto-hydrodynamic models to analyze how AGN emission line profiles depend on viewing and launching angles, comparing results with observational data to constrain the structure of the torus.

Contribution

It introduces an improved model linking wind launching angles and viewing angles to emission line profiles, providing new constraints on the AGN torus geometry.

Findings

Larger torus half-opening angles require smaller wind launching angles to match observations.

Beyond a 47° half-opening angle, no wind launch angle can reproduce observed linewidth dispersions.

Warped disc models yield similar constraints as traditional torus models.

Abstract

We study AGN emission line profiles combining an improved version of the accretion disc-wind model of Murray & Chiang with the magneto-hydrodynamic 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? degrees, increasingly larger wind launching angles are required to match the observational constraints. Above a half-opening angle of about 47? degrees, no wind launch angle (within the maximum allowed by the MHD solutions) can match the observations. Considering a model that replaces the torus by a warped disc yields the same constraints obtained with the two other models.