The animation of this figure is of the step-by-step subtraction process, showing how the shape of the pixel histogram changes for the corresponding continuum-subtracted [O III] images as the continuum-image scale factor is increased from 0 to 0.36. The point of optimal subtraction can be identified around scale factor ≈0.18. The video duration is 9 s.

(An animation of this figure is available.)

The video/animation of this figure is available in the online journal.