PPV diagram from the combination of one- and two-layer model fitting. The bottom x-y image is the CH₃CN J=12-11 K=3 integrated intensity map. Above it, each position can have one or two velocities. The color of data points indicates the kinematic component from clustering. The two cyan vertical lines indicates the positions and the systemic velocities of VLA4A (7.36 km s⁻¹) and VLA4B (9.33 km s⁻¹).