From left to right: (a) Distribution of the total integrated N₂H⁺ (7–6) emission detected by APEX-SEPIA660 (red contours; this work) superposed to the N₂ H⁺ (1–0) emission observed by ALMA (colour scale; Hacar et al. 2018) both convolved into a resolution of 10″. (b) Comparison between N₂H⁺ (7–6) (red contours) and C¹⁸O (6–5) (black contours) emission as function of the gas kinetic temperature (colour scale, Hacar et al. 2020). Both N₂ H⁺ and C¹⁸ O contour levels are similar to those displayed in Fig. 1. (c) line peak ratio (colour scale) plotted over the total integrated intensity N₂H⁺ (1–0) (grey scale). For reference, the position of the Trapezium (white stars) and the Orion BN source (yellow star) are displayed in all maps. The first contour of the N₂ H⁺ (1–0) emission (W(N₂H⁺(1−0)) = 1.0 K km s⁻¹,white contour) is also indicated in panels a and c. The black crosses in panel a indicate the position of the representative spectra shown in Fig. 3.