Mean dynamical effects as a function of dark matter density. The mean dynamical effects of turbulence and thermal motion in the cosmic fluid, as well as the gravitational effect, the cosmic expansion effect, and their combined effects, are represented by Q_turb, Q_th, Q_grav, Q_exp, and Q_tot, respectively. Panels (a) to (f) are for z = 4 to 0, respectively. We chose the units of velocity, ∇, and time as km/s, h/Mpc, and (Mpc/h/km)s, respectively, which results in the vertical label shown in the figure.