Position-velocity diagram along the pseudoslit crossing the supernebula, and oriented along the maximum velocity gradient, as shown in Fig. 6. Velocities are shown relative to v_sys = − 390 km s^-1 (Schwartz & Martin 2004). The vertical dashed lines indicate the region within which both C2 and C3 follow the same steep gradient. We interpret this as evidence of an outflow from the supernebula clusters.