Model of the NaCl rotating disk. Top: schematic representation of the geometry and density distribution of the NaCl-emitting region adopted in our model (Sect. 5.2 and Table 3). The plot is a cut of this region by a plane that contains both the line of sight and the rotation axis of the nebula. The latter is oriented in the sky along PA ~ 25°. The linear size of the 20 mas beam (at d = 1500 pc) of our ALMA NaCl maps is shown in the lower-left corner. Bottom: synthetic NaCl ALMA data from our LTE model plotted as in the bottom panels of Fig. 3. The synthetic cubes of the NaCl (υ = 0, J = 20–19) transition are shown in Fig. A.2.