Examples of the emission line fitting technique used. The left panels show examples of the Gaussian fits obtained using MPFIT to J1300+54 and J1347+12, which have the narrowest and broadest line profiles in the sample. The black line shows the data and the red line shows the sum of the Gaussian components which are denoted in shades of blue and green. The red crosses show pixels that were masked out of the fit. The right panels show the corresponding non-parametric values derived from the emission line models. All the emission line fits are shown in Appendix https://zenodo.org/records/11965868.