Dependence of ⟨V_z⟩ (km s ⁻¹) on the azimuth ω (°) in the cavity.¹²CO (3–2) is in black, ¹³CO (3–2) in red and C¹⁸O (3–2) in blue. The red curve is a fit of a sine function to the ¹³CO (3–2) data (see text). We use a blank space when no good data are available (no emission) in the ring. The magenta curves show the expected Keplerian velocity around a single star of 1.36 M_⊙. The green curve in panel f shows the best-fit velocity curve when infall motions are allowed, superimposed on the ¹³CO velocity.