As Fig. 7, but an edge-on view. Oxygen and nitrogen are predominantly doubly ionized close to the ionizing sources, and singly ionized only in the outer part of the ionized region. Thus, and because of radiation hardening and therefore higher temperatures, the maximum of the line ratios [N II]∕H β and [O II]∕Hβ occurs at larger heights above the galactic plane. For the cases with a clumping factor of f_cl = 5 the [O III]∕Hβ ratio rises up to a height of approximately 700 pc above the galactic plane and drops again at larger distances.