Spectra extracted for our study in (left to right) H¹³CN (1 − 0), HC¹⁵N (1 − 0), ¹⁵NNH⁺ (1 − 0), N¹⁵NH⁺ (1 − 0) and N₂H⁺ (1 − 0); from top to bottom, the spectra extracted in the E, NW, NE, S and FIR3 regions. The CASSIS fits are superimposed in red. The dashed black line represents the V_LSR value for thissource, which is 11.4 km s⁻¹. The blue lines represent the location of the HFS components for N₂H⁺ and its ¹⁵N isotopologues.