Intensity weighted velocity (first moment) maps of the OCS and H₂CO emission observed towards VLA 2a, VLA1a and VLA1b. The contours show the 10, 20, 30, and 40σ contours of the 48 GHz continuum emission. The solid grey line shows the position angle of the outflow as outlined in Fig. 4, and the dashed black line shows the direction of the velocity gradients indicated here. The colour scales in each panel are identical, which indicates that the H₂CO has a larger velocity gradient than the OCS, since they emit on roughly the same spatial scales.