Continuum emission, CO(2−1) integrated flux maps of Mrk 509 and the CO(2−1) spectrum extracted from the continuum-subtracted clean data cube. Left panel: 1.2 mm continuum map of Mrk 509. Regions with emission below 5σ have been blanked. The synthesised beam (0.396 × 0.343 arcsec²) is shown by the grey filled ellipse. Central panel: CO(2−1) integrated flux map, where a mask with threshold of 3σ has been applied. Black contours show the 1.2 mm continuum emission at (5, 30, 100) × σ. The synthesised beam is shown in the bottom left corner. Right panel: CO(2−1) spectrum (black crosses) extracted from the continuum-subtracted clean data cube from the regions where emission is above 3σ. The solid red line shows the multi-Gaussian fit; the magenta lines show the three Gaussian components.