Collisional and Thermal Emission Models of Debris Disks: Toward Planetesimal Population Properties

Abstract

Debris disks around main-sequence stars are believed to derive from planetesimal populations that have accreted at early epochs and survived possible planet formation processes. While debris disks must contain solids in a broad range of sizes—from big planetesimals down to tiny dust grains—debris disk observations are only sensitive to the dust end of the size distribution. Collisional models of debris disks are needed to ‘‘climb up’’ the ladder of the collisional cascade, from dust toward parent bodies, representing the main mass reservoir of the disks. We have used our collisionalcodetogeneratefivedisksarounda Sun-likestar,assumingplanetesimalbeltsat3,10,30, 100,and 200 AU with 10 times the Edgeworth-Kuiper Belt mass density, and to evolve them for 10 Gyr. Along with an appropriate scalingrule,thiseffectivelyyieldsathree-parametricsetof referencedisks(initialmass,locationof planetesimalbelt, andage).For allthe disks,wehavegeneratedspectral energydistributions (SEDs),assuming homogeneousspherical astrosilicate dust grains. A comparison between generated and actually observed SEDs yields estimates of planetesimalproperties(location,totalmass,etc.).Asatestandafirstapplicationof thisapproach,wehaveselectedfivedisks aroundSun-likestarswithwell-knownSEDs.Infourcases,wehavereproducedthedatawithalinearcombination of two disks from the grid (an ‘‘asteroid belt’’ at 3 AU and an outer ‘‘Kuiper Belt’’); in one case a single, outer component was sufficient. The outer components are compatible with ‘‘large Kuiper Belts’’ of 0.2Y50 Earth masses (in bodies up to 100 km in size) with radii of 100Y200 AU. Subject headingg circumstellar matter — planetary systems: formation — Kuiper Belt — stars: individual (HD 377, HD 70573, HD 72905, HD 107146, HD 141943)