Pressure threshold contours. The map shows the same morphological environment masks as in Fig. 3. Overlaid are HCN contours in grey and ⟨P_DE⟩ contours at $⟨P_{\text{DE}}⟩=3.8\times {10}^5{k}_{\mathrm{B}}\mathrm{K}{\mathrm{cm}}^{-3}$ (black) and at $⟨P_{\text{DE}}⟩=1.6\times {10}^6{k}_{\mathrm{B}}\mathrm{K}{\mathrm{cm}}^{-3}$ (red). The pressure contours represent the threshold values in the pressure relations discussed in Sect. 4.3.