Post-giant impact planetesimals sustaining extreme debris discs

Extreme debris discs can show short-term behaviour through the evolution and clearing of small grains produced in giant impacts, and potentially a longer period of variability caused by a planetesimal population formed from giant impact ejecta. In this paper, we present results of numerical simulations to explain how a planetesimal populated disc can supply an observed extreme debris disc with small grains. We simulated a sample of giant impacts from which we form a planetesimal population. We then use the N-body code REBOUND to evolve the planetesimals spatially and collisionally. We adopt a simplistic collision criteria in which we define destructive collisions to be between planetesimals with a mutual impact velocity that exceeds two times the catastrophic disruption threshold, V*. We find that for some configurations, a planetesimal populated disc can produce a substantial amount of dust to sustain an observable disc. The semimajor axis at which the giant impact occurs changes the mass added to the observed disc substantially, while the orientation of the impact has less of an effect. We determine how the collision rate at the collision point changes over time and show that changes in semimajor axis and orientation only change the initial collision rate of the disc. Collision rates across all discs evolve at a similar rate.