Physical conditions of the gas of the emission of CH₃CN associated with the GGD 27-MM2(E) molecular outflow as a function of the distance to the central source. (a) Excitation temperature. (b) Column density. (c) Line width. (d) Velocity of the gas. Error bars are derived from the model (see the main text for more details). Orange and green squares show results from a simultaneous fitting of two kinematic components. The orange squares are probably associated with weak/mild shocks from the expanding outflow walls, whereas the green squares are possibly linked with a more violent shock between the fast wind and a dense cloudlet (MC source), whose position is marked by a dashed vertical line at about $3_{\cdot }^{\mathrm{\prime }\mathrm{\prime }}5$.