Kernel density estimate representation of the distribution of p-NH₃ column density with N(H₂) in the cores (in red) and shell-1 (in blue), as defined in Sect. 4.4 and shown in Fig. 8. The straight lines show the best linear fit to the data in the corresponding region. For comparison between the regions, the linear fit to the data in the cores (red line) is also shown in the plot for shell-1. The slopes of the linear fits indicate the fractional p-NH₃ abundance (with respect to H₂) in the region, which is shown in the top-left corner.