PV diagrams of the Herschel and IRAM observations along the SW-NE strip. The C ii diagrams comes from Pilleri et al. (2012a). The double-peaked structure of the CCH lines is due to two hyperfine components of the same line, while the strong dip in both CH and [C ii] are partially due to self-absorption. The white line in the top-right corner of each diagram represents the HPBW of the observation. The black dotted line indicates v_LSR = 11.5   km   s^-1.