Initial particle distributions (grayscale) in our kinematical models projected on the plane of the sky, which represent the maps of the column density of our model envelopes. Panel a: case of the axisymmetric envelope model. Panels b–e: cases of the asymmetric envelope models with different V_rel as labeled at the upper left corners. Panel f: model of the asymmetric envelope with the two V_rel, V_rel of 0.9 and 0 km s⁻¹ on the far and near sides of the envelope, respectively. Contours show the fraction of the total number of the particles, starting from 10% in steps of 20%.