Top: main components identified in our simple model (see Sect. 4.1). Bottom (below the dotted line): Representative image of the equatorial density distribution as seen with the actual inclination of the equator. This image is a very simplified representation to facilitate interpretation, in which the latitude density distribution is not accounted for. The projection of the equatorial velocity in the direction to the observer is also represented (directly taken from the velocity vectors in Fig. 6, top). Again this is only illustrative because the off-equator movements are not considered. Downward arrows represent gas approaching the observer (relatively negative LSR velocities), while arrows pointing upward mean that the gas recedes from us (relatively positive LSR velocities).