Intensities at the mean velocities (top row), mean velocities (middle row), and linewidths (bottom row) obtained from the Gaussian fit for Model 1 (left column), Model 2 (middle column), and the HCO⁺ (J = 4→3) (right column). For all figures: The ellipse in the right panel represents the size of the beam for the observations, which we used to convolve the images of the models. The colour bar on top of the left panel applies to the three sub-images. The coordinate system is rotated by 24° (see details in text).