Panel a: The radial velocity profile of the main component along the G035.39 filament, starting at its southernmost point. The solid black line shows the radial velocities fit at the intensity ridge of the IRDC. The width of the solid black line represents the fitting uncertainty at each point. The vertical dotted lines mark the projected locations of the massive protostellar cores from Nguyen Luong et al. (2011). Panel b: Same as a, but for the velocity dispersion profile along the IRDC ridge. The yellow shaded region denotes the spread area given by two standard deviations of all σ values in the main velocity component.