Kinematics of the helix stream. (Left) ¹²CO(1–0) PV diagram of the helix stream along the cut AB indicated in Fig. 3 overlaid with the position-velocity loci of Hi-GAL prestellar (blue dots) and protostellar (red triangles) clumps discussed in Section 3.4. (Right) The ¹³CO (2–1) PPV plot of the helix stream generated from spectral decomposition using GAUSSPY+. Each velocity component is colour coded according to its velocity dispersion. Ellipse marks the shell feature discussed in Section 4.1.