contaminating narrow-line components. Here we are only concerned with the region immediately surrounding [H$\alpha$]{} and [H$\beta$]{}. For [H$\alpha$]{}, as outlined in Greene & Ho (2004; see also Ho et al. 1997), we begin by constructing a model for the narrow components using the [\[\]]{} $\lambda \lambda$6716, 6731 lines. In short, a multi-Gaussian model is fit to the [\[\]]{}doublet, and then shifted and scaled to fit the [H$\alpha$]{}+[\[\]]{} $\lambda\lambda$6548, 6583 complex. The relative positions of the narrow [H$\alpha$]{} and [\[\]]{} lines are constrained by their laboratory values, and the relative ratio of the two [\[\]]{}components is fixed to 2.96. We then fit the broad component of [H$\alpha$]{} with as many Gaussian components as needed to provide a statistically acceptable fit. This method provides the needed flexibility to reproduce highly non-Gaussian, asymmetric profiles, but we attach no physical significance to the individual components.

The fitting procedure for [H$\beta$]{} is similar to that outlined above; in this case the narrow-line contamination comes from the narrow component of [H$\beta$]{} and [\[\]]{} $\lambda\lambda$4959, 5007. Because of their proximity, we first experimented with modeling the narrow [H$\beta$]{} component using [\[\]]{} as a template, but could not reliably obtain a satisfactory fit. The mismatch stems partly from 