Example fit for the doublets studied in this study for source 77155. On the left is the Mg IIλλ2796, 2803 fit with the residuals at the bottom. The Mg Iλ2852 line is also visible in this slice of the spectrum. In the centre, the fit for Fe IIλλ2586, 2600, also with the residuals of the fit at the bottom. On the right, using the same schedule, the case of Fe IIλλ2374, 82 with a low S/N ratio. You can also see the C II] λ2325 in emission and Fe IIλ2344 in absorption.