Variations on debris disks. II.

Despite the large number of Plutos produced in many calculations, icy planet formation is inefficient. At the end of the main sequence lifetime of the central star, Plutos contain less than 10% of the initial mass in solid material. This conclusion is independent of the initial mass in the disk or the properties of the planetesimals.

Debris disk formation coincides with the formation of planetary systems containing Plutos. As Plutos form, they stir leftover planetesimals to large velocities. A cascade of collisions then grinds the leftovers to dust, forming an observable debris disk.

In disks with small (<~1-10km) planetesimals, collisional cascades produce luminous debris disks with maximum luminosity ~10-2 times the stellar luminosity. Disks with larger planetesimals produce debris disks with maximum luminosity ~5x10^-4^ (10km) to 5x10^-5^ (100km) times the stellar luminosity. Following peak luminosity, the evolution of the debris disk emission is roughly a power law, f{propto}t^-n^ with n~0.6-0.8.

Observations of debris disks around A-type and G-type stars strongly favor models with small planetesimals. In these models, our predictions for the time evolution and detection frequency of debris disks agree with published observations. We suggest several critical observations that can test key features of our calculations.