Same as Fig. 3, but for the comparison between HCNH⁺ and CN. For CN, N_tot (left panel), [CN] (middle panel), and FWHM (right panel) are derived from observations of the ¹³ CN N = 2− 1 line at ~217 GHz, published in Fontani et al. (2015b). N_tot (HCNH⁺) and N_tot (CN) are averaged within the same beam of ~11′′, and left-pointing triangles are upper limits on N_tot (CN), while down-pointing triangles are upper limits on N_tot (HCNH⁺). [HCNH⁺] and [CN] areaveraged within a beam of 28′′.