Left: sketch of the biconical geometry adopted in our model (Sect. 4). The equatorial plane is oriented in the sky along PA = 45° and is seen edge-on. Right: two-dimensional representation of the density law adopted (Table 2). Contour levels are 2.5 × 10⁵, 5 × 10⁵, 10⁶, 5 × 10⁶, 10⁷, and 5 × 10⁷ cm⁻³. Dotted linesdelimit the different model components. The neutral disk is not probed by our ALMA observations.