Integrated intensities of the HCN 1–0 line emission. Left panel: the red-shifted wing emission from 350 to 990 km s^-1. The grayscale range is from 0 to 0.7 Jy km s^-1 (beam )^-1 and the contours start at 0.098 Jy km s^-1 (beam)^-1 with steps of 0.0998 Jy km s^-1 (beam)^-1. Middle panel: the blue-shifted wing emission from  −990 to  −350 km s^-1. Same grayscale and contours as for the previous panel. Right panel: the total (from  − 990 km s^-1 to 990 km s^-1) integrated HCN 1–0 line emission from Mrk 231. The grayscale range is from 0 to 8 Jy km s^-1 (beam)^-1 and the contour levels are 0.45 Jy km s^-1 (beam)^-1  ×  (1,3,5,7,9,11,13,15,17,19). The thick white crosses mark the peak of the integrated HCN 1–0 line emission and the thinner crosses indicate the VLBI position (see footnote to Table 1) and 1′′ = 870 pc. Hatched ellipse indicates beam size and orientation.