Disk selection. The ratio of the disk-averaged rotational velocity to the disk-averaged radial velocity dispersion, ⟨V_rot⟩/⟨σ_r⟩, is plotted against the ratio of the disk radius to the disk height, R_d/H_d, for all 1098 snapshots belonging to 34 VELA galaxies with the round blue points. Of these, 425 snapshots satisfy the conditions R_d/H_d > 3 and V_rot/σ_r > 1 at all r, the distance from the galactic center in cylindrical coordinates, and they are selected as rotation-supported disks (highlighted by the red stars). Here, V_rot and σ_r are the average rotational velocity and the radial velocity dispersion of cold gas as a function of r, respectively. The gray dashed vertical and horizontal lines indicate R_d/H_d = 3 and ⟨V_rot⟩/⟨σ_r⟩ = 1, respectively. Some of the blue points with R_d/H_d > 3 and ⟨V_rot⟩/⟨σ_r⟩> 1 do not satisfy the condition V_rot/σ_r > 1 at all r. As such, they are not in the disk galaxy sample.