Spectrum of N₂D+ (3–2) towards C2c1a (upper panel) and C2c1b (bottom panel). Shown as coloured lines is the spectrum averaged within the boundary of the cores (see Fig. 1), and the coloured shaded regions indicate the uncertainty (rms). Shown in grey is the N₂D+ (3–2) hyper-fine fit to the spectrum assuming optically thin (τ = 0.1) conditions (faded grey curves show the individual hyperfine components of the fit), with the fit parameters shown in the upper right of each panel. The faded spectrum below each profile is the residual of the fit (offset by −0.6 K). Figures A.1 and A.2 show moment and channel maps of the N₂D⁺ (3–2) emission across the region, respectively.