Line Width and Spectral Index Distributions as Evidence for Axisymmetry in the Broad Line Regions of Active Galaxies

Abstract

We propose that the scatter in line width versus luminosity of the BLR of AGN arises from a dependence on the line of sight to an axially symmetric BLR. Adopting a simple model for the line width as a function of luminosity and angle, and convolving this with the observed luminosity function, allows us to predict a line width distribution consistent with the available data. Furthermore, we use the relation between the equivalent width of a line and the luminosity in the continuum to predict an observed correlation between line width and equivalent width. The scatter on this correlation is again provided by angular dependence. We also show a viewing angle dependence can produce the X-ray spectral index distribution. The results have applications as diagnostics of models of the broad line region and in cosmology.