(a) Map of the difference between the velocity of the C³³ S(2-1) line and the systemic LSR velocity of the HMC (96.5 km s⁻¹ ). The white contours correspond to 0 km s⁻¹. The black contours are the same as in Fig. 6. The dotted pattern outlines the approximate border of the HMC. (b) Same as panel a, for the difference between the velocity of the H39α line and that of the HMC. (c) Same as panel a, for the difference between the velocity of the H39α line and that of the C³³ S(2-1) line. (d) Same as panel a, for the difference between the velocity of the H39α line and that of the absorption dip of the CN(1-0) line. the HMC. The synthesised beam is shown in the bottom-right corner.