[N II]_λ 6583/Hα vs. [S II]_λ 6717/Hα diagnostic diagram for IC1553. Colours represent height with respect to the midplane, equally from above and below the plane. Vertical dashed lines are the theoretical ratios obtained from Eq. (1) at a constant T_e (6, 7, 8, and 9 in units of 10³ K). Solid lines represent the theoretical ratios from Equations (1) and (2) for a fixed S⁺/S (0.25, 0.5, and 0.8, respectively). The circles indicate the line ratios obtained by integrating the fluxes along the major axis at a certain z. Stars, triangles, and squares indicate the line ratio at a certain z for MAD = −2.5, 0, and 3 kpc, respectively.