Effect of the SN bubbles on the profile of the radial acceleration a_rad. A positive (negative) radial acceleration indicates that the vector points away from (toward) the galaxy center. At the beginning of the simulation, before SNe appear, the profile is smooth (top). Later, the radial acceleration depends on the position within the galaxy (bottom). The images are 2D histograms of individual stellar particles in the simulation GDw1e8_e3. Only particles near the disk plane are shown here. The upper panel also shows that the gravitational potential of the galaxy is not harmonic (i.e., the acceleration is not ∝r).