Position–velocity diagrams of H¹³CN J = 4–3, CS J = 7–6, HCN J = 4–3, and HCO⁺ J = 4–3, using v_lsr = 6.0 km s⁻¹. Contours are spaced linearly between 5 and 100% of the peak emission, in five steps. The PV diagrams are made along the direction of the velocity vector andthe offset is the distance to the rotation axis (Fig. 4). The emission center, as defined in Sect. 4, is the intersection of the rotation axis and velocity vector. The equation v_lsr = 6.0 km s⁻¹, derived in Sect. 4, matches the H¹³CN J = 4–3 emission well, while the large-scale emission seen in HCN J = 4–3, CS J = 7–6, and HCO⁺ J = 4–3 are better matched by 5.5 km⁻¹ (Hatchell et al. 1999). All the data shown in this figure are from the combined dataset.