Moment zero maps (top panels) and integrated emission profiles (bottom panels) for the lines observed with the NOEMA interferometer: from left to right, ¹³CO J=2-1, C¹⁷O J=2-1, C¹⁸O J=2-1, HCO⁺ J=2-1, and HCN J=2-1. For the moment zero maps, the intensity is given in Jy beam⁻¹. Contours are drawn at 10% to 90% by intervals of 10% of the maximum in the respective map. The contour step, 10% of maximum, in Jy beam⁻¹, is given at the bottom of the panel. The colour scale is fixed between −10% and 100% of the maximum emission. Offsets are given along the major symmetry axis of the nebula (the maps have been rotated by 49° so the revolution axis of the nebula, at PA 311° is in the vertical direction). Integrated emission profile fluxes are given in Jy vs. LSR velocities in km s⁻¹. To keep the same flux scale in all five panels, spectra other than that of ¹³CO J=2-1 have been multiplied by the factor indicated in the top right corner.