From left to right: (a) N₂H⁺ (1–0) integrated emission (see also Hacar et al. 2017a), (b) I(HCN)-to-I(HNC) line intensity ratio (see also Fig. 1), (c) gas kinetic temperature map derived using NH₃ measurements (Friesen et al. 2017), and (d) gas kinetic temperature map derived using the proposed I(HCN) ∕I(HNC) as a temperature probe according to Eqs. (3) and (4) (this work). For comparison, we indicate the intensity contour with I(N₂H⁺) = 1.5 K km s⁻¹ in panels b–d. Circles and stars are similar to Fig. 1.