Simulated shell structure 2.2 Gyr after the decay of the cannibalized galaxy. Only the particles originally belonging to the cannibalized galaxy are taken into account. Top: surface density map; middle: the LOSVD density map of particles in the  ± 1 kpc band around the collision axis; bottom: histogram of galactocentric distances of particles. The angle between the radial position vector of the particle and the x-axis (the collision axis) is less than 90° for the blue curve and less than 45° for the red curve. The horizontal axis corresponds to the projected distance X in the upper panel, to the projected radius R in the middle panel, and to the galactocentric distance r in the lower panel.