Comparison of observations with the VELA disk galaxy sample. Same as in Figure 14 except now ⟨V_r⟩/⟨V_rot⟩ is plotted against the redshift, z, and the circles corresponding to the simulated disks are color coded by their gas fraction, f. The observations agree with the stream-averaged radial velocities found in the simulated disks (middle panels). The disk-averaged (left panel) and non-stream-averaged (right panels) radial velocities from the simulations typically have much smaller magnitudes and barely agree with the observations.