p-v diagrams along cuts perpendicular to the galactic plane at E2 (top), the (0, 0) position (middle) and W2 (bottom). Color scale and black contours correspond to the H(41)α emission. White contours are intensities of the CN 1 → 0, CS 3 → 2 and N₂H⁺1 → 0 lines. First contours (3 × σ) and steps are 10 mJy/beam for CN and CS, 2 mJy/beam for N₂H⁺, and H(41)α. The CN 1 → 0/N₂H⁺1 → 0 line intensity (in T_b units) ratio along these cuts is shown in the right column. The images have been degraded to a angular resolution of 3.8″ and a velocity resolution of 12 km s^-1 to show this line ratio. Vertical lines indicate the position of the velocity components discussed in the text.