Results of the analysis of the ammonia maps in L1544. Central panel: ammonia ¹⁴N/¹⁵N map. The contours show the total gas density at levels N(H₂) = [1,1.5,2,2.5] × 10²² cm⁻², obtained from Herschel SED fitting (Spezzano et al. 2017). The black circles show the three offsets (labelled with capital letters) where we compute average spectra to improve the S/N. The averaged ¹⁵NH₃ (1,1) lines are shown in the surrounding panels (black: observations, red: best-fit models, obtained as described in Appendix B). These panels are labelled in their top left corner, whilst in the top right corners we indicate the measured ¹⁴N/¹⁵N.