Integrated intensities of HCN 3−2, HCO⁺ 3−2, HCN 4−3, and HCO⁺ 4−3 between −400 and 400 km s^-1 around the systemic velocity (see Sect. 3.2). Contours represent 3, 6, 10, 20, 40, 80, 150, and 300 σ levels where 1σ = 0.35 Jy km s^-1 beam^-1. Peaks of continuum emission (Fig. 1) are indicated with crosses. The region shown is the same as in Fig. 1. The blue arrows in the HCO⁺ 3−2 panel indicate the direction (PA = 30° and 115°) of the P-V cuts in Fig. A.2.