Position velocity maps of source A, along the direction shown in the rightmost panel of Fig. C.2, for the three lines studied. From left to right: CH₃OCHO-A, CH₃OCHO-E, and H₂CCO. Contours are drawn to  − 3, 3, 10, 22, 39, 61, 88, 120, and 157 times the rms noise, 4.5 mJy   beam^-1, where negative contours are plotted using dotted lines. The red dashed line and red solid circle show the 8 km   s^-1   arcsec^-1velocity gradient and position of source A (V_LSR = 3.4 km   s^-1), respectively. Notice that in all panels an adjacent molecular transition line is marked with a vertical blue line, which can also be identified in Fig. 2. The spatial resolution is shown at the bottom right corner.