Channel maps of the data shown as a spectrum in Figure 1 (left) at the same velocity resolution. Frequencies increase with channel number from left to right, i.e., red to blue. The peak channels of the redshifted HCN, HCO ⁺, and HC ₃N lines are indicated. Contours are shown at (−3, −2, 2, 3, 4, 5, 6, 7, 8) σ (1σ = 0.95 mJy beam ⁻¹). The beam size (4 5×3 6) is shown in the bottom left corner. The cross indicates a position of 08 ^h31 ^m41 70, +52°45′17 5 between the CO lens images (Riechers et al. 2009).