Longitudinal effective velocity dispersion and corresponding are shown using the same molecular transitions and line colours as shown in Fig. 13. Also plotted are M_line-dust and M_line-13CO (and corresponding ). Except for ¹³CO-based measurements, the values are averaged over the same width and length as in Fig. 4, whereas ¹³CO-based values are averaged over a 2.82 pc scale (i.e. 1.41 pc either side of the ridge). The y axis on the left portrays the velocity dispersion and the y axis on the right is the M_line. The axis appears stretched by a square root scale since, in the critical case, σ_eff ∝M_line^0.5. Translucent regions describes the 1-sigma uncertainty values each molecular line tracer. 1-sigma uncertainty values are not shown for M_line-13CO.