[S ii] 6716 Å (b) and 6731 Å (r) lines and single Gaussian profiles fits to the spectrogram C of Fig. 3. The positions (west) of the profiles are indicated. Two pixels (one tick mark) is 70 km s^-1. The vertical dashed lines illustrate the velocity shift; the reversal occurs near 60−70′′. From 45 to 85′′, the line intensity decreases by a facter of  ~10, with a corresponding increase in noise. (The FWHM of a weak skyline (near Hα) is 2.5 pixels.)