NIR spectra from −9d to +5d are normalized to a level continuum over the region 0.98–1.08 μm and zoomed in on the blueshifted Mg II λ1.0927 feature. The velocity space on the bottom axis is calibrated to the C I λ1.0693 line. C I flattens the blue wing of the Mg II feature from −7.4d to +3.2d. The spectrum closest to t(B_max) (−0.4d) is compared to models in Figure 5 and discussed in the text. The dotted line shows the approximate shape of the line profile predicted by the model when C I is absent. The dashed line corresponds to the absorption minimum of C I in models that fit the data well and the dash–dotted line marks the absorption minima for Mg II.