Trihydrogen isotopologue maps with IRAC-1 image. Left: IRAC-1 image at 3.6 μm. The white contours trace ortho-H₂D⁺. The filled grey contour marks the strongest emission (contours from 0.10–0.34 by 0.06 [=2.6σ] K km s⁻¹). Right: para-D₂H⁺ and ortho-H₂D⁺ maps. Same map of para-D₂H⁺ (black contours) as in Fig. 1, but superimposed on the ortho-H₂D⁺ map (colour scale, plus white contours as in left panel). The yellow, black, and red crosses are as in Fig. 1. The D₂H⁺, H₂D⁺, and N₂H⁺ spectra along the cut traced by the dashed line are displayed in Fig. 3.