Combined ¹⁴N/¹⁵ N ratios in N₂H⁺ in regions defined by Fontani et al. (2020) (red) and in regions defined by our work (blue) overlaid onto N₂H⁺ (1–0) emission from Fontani et al. (2020) (colour scale), with the blue values representing the average of those presented in Table 5; red triangles show locations of continuum emission sources in FIR4 as identified by Neri et al. (in prep.). The wedge on the right indicates the range of flux density (Jy beam⁻¹). The ellipse in the bottom-left corner represents the ALMA synthesised beam.