|
Description
We describe calculations for the formation of icy planets and debris disks at 30-150AU around 1-3M_{sun}_ stars. Debris disk formation coincides with the formation of planetary systems. As protoplanets grow, they stir leftover planetesimals to large velocities. A cascade of collisions then grinds the leftovers to dust, forming an observable debris disk. Stellar lifetimes and the collisional cascade limit the growth of protoplanets. The maximum radius of icy planets, r_max_~1750km, is remarkably independent of initial disk mass, stellar mass, and stellar age. These objects contain <=3%-4% of the initial mass in solid material. Collisional cascades produce debris disks with maximum luminosity ~2x10^-3^ times the stellar luminosity. The peak 24um excess varies from ~1% times the stellar photospheric flux for 1M_{sun}_ stars to ~50 times the stellar photospheric flux for 3M_{sun}_ stars. The peak 70-850um excesses are ~30-100 times the stellar photospheric flux. For all stars, the 24-160um excesses rise at stellar ages of 5-20Myr, peak at 10-50Myr, and then decline. The decline is roughly a power law, f{propto}t^-n^ with n~0.6-1.0. This predicted evolution agrees with published observations of A-type and solar-type stars. The observed far-IR color evolution of A-type stars also matches model predictions.
|
