Best-fit parameters from the ALI modelling of the observed N₂H⁺ maps, yielding results as shown in Fig. 4. Modelled data use an intensity threshold of 3σ of the rms noise for both lines. Upper row: from left to right, spatial distributions for the gas column density, N(H₂), the kinetic gas temperature, T_kin, the gas volume density, n(H₂) and the relative molecular abundance, X(N₂H⁺) = n(N₂H⁺)/n(H₂). Lower row: from left to right, spatial distributions for the line centre optical depth of the (3−2) and (6−5) lines, the N₂H⁺ column density, N(N₂H⁺), and the residuals of the radial velocity fits Δv in km s^-1. Spatial scales are in arcsec and the colour coding is given by the vertical bars next to each frame.