Model Spectral Energy Distributions of Circumstellar Debris Disks

We present results of a study aimed at deriving fundamental properties of circumstellar debris disks from observed infrared to submillimeter spectral energy distributions. This investigation is motivated by increasing telescope/detector sensitivity, in particular the expected availability of the Space Infrared Telescope Facility (SIRTF) followed by the Stratospheric Observatory for Infrared Astronomy (SOFIA), which will enable detailed studies with large source samples of late stage circumstellar disk and planetary system evolution. We base our study on an analytic model of the disk density distribution and geometry, taking into account existing constraints from observations and results of theoretical investigations of debris disks. We also outline the effects of the most profound characteristics of circumstellar dust including the grain size distribution and dust chemical composition. In particular we find that an increasing iron content in silicates mainly causes an increase of the dust absorption effiency and thus increases the dust reemission continuum. Furthermore, the influence of the sp/sp hybridization ratio in carbon grains on the spectral energy distribution is examined. We investigate the influence of various parameters on the resulting dust scattering and absorption/reemission spectral energy distribution and discuss the possibility for distinguishing between different disks from their infrared to submillimeter spectra. The strength and shape of amorphous silicate may be particularly diagnostic of debris disk evolutionary stages. Since the appearance of these features at 10μm and 20μm depends on the relative abundance of small grains and therefore the minimum grain size and slope of the grain size distribution they can be used to trace recent collisional processes in debris disks. Thus, debris disk surveys containing statistically large numbers of objects should reveal the likelihood of collisions and therefore the evolution of dust/planetesimals in debris disks. The