Schematic of particle deletion. Shown in a 50 × 50 kpc box. The deletion regions (exaggerated by a factor of 10 from that used) are shown with a red dashed line (for deletion of all particles) and green dotted lines (deletion of stellar/dark matter particles). Particle positions and velocities are shown with arrows. Particles that would be deleted on the next time step if they were stellar or dark matter particles are shown in green. Particles that would be deleted on the next time step regardless of their type (gas, stellar, or dark matter) are shown in red. The remaining particles, which are not deleted regardless of type, are shown in black.