Power-law density profiles discussed for two scenarios in Sect. 4.3. In the left panel, the IRAS 4A position is taken as the reference and r_AB indicates the 4A-4B distance. In the right-hand panel, the individual envelope profiles are shown. This panel includes a typical drop-abundance profile, with an outer abundance X₀, a freeze-out abundance X_D, and an inner abundance X_in. In an anti-jump profile, the evaporation jump in the inner envelope is lacking.