Numerical simulations of Neptune's arcs show that self-gravity between macroscopic are particles can prevent interparticle impacts and thereby stabilize their resonant confinement by Galatea, a satellite of Neptune, Stable subkilometer are particles provide a source for replenishing the observed dust and explain the clumpy substructure seen in arcs, A few confining kilometer-sized particles between the major are components can account for the observed are widths spanning several resonance sites. The modeled distribution of dust is consistent with observations and helps to explain how embedded satellites may affect the structure and evolution of planetary ring systems.