Individual profiles where the spectral shape of the C iv  1548 Å is different from the shape of the co-local and simultaneously recorded C iv  1550 Å line. The vertical lines show the zero velocity wavelength of the 1548 Å and 1550 Å spectral lines. The interval between 1548.9 Å and 1549.4 Å is due to the too-short spectral windows used during the rasters. Panels a) to d) are recorded over Region 1 while panels e) and f) over Regions 2 and 3 respectively. Data points are represented with a thick histogram line. The thin lines represent the Gaussian functions needed to fit the data.