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Session 5 - Accretion and Outflows in YSOs.
Display session, Wednesday, January 07
Exhibit Hall,

[5.03] A Model of Scattering from Dust in Proto-planetary Disks applied to O.1" resolution U. of Hawaii Adaptive Optics Images of the Disk around Young Stars

D. E. Potter (U. Hawaii), L. Close (U. Hawaii), F. Roddier (U. Hawaii)

We present a method for using the infrared extinction profile and observed scattered infrared radiation from dust in proto-planetary disks to obtain constraints on the dust grain size distribution, density profile, inclination, and extent of the disk. Our method utilizes a Mie scattering algorithm which calculates the exact scattering angle probabilities for light incident on a homogeneous sphere. The dielectric properties of the dust used in the modeling are that of a realistic mix of silicate, amorphous carbon, graphite, and vacuum. The code produces disk images and extinction values from given inclination angles, dust size and density distributions, wavelengths, and flaring profiles. Parameter fitting routines can thus be carried out between these models and high resolution observations to constrain the parameter values of the observed disks. \bigskip The recently obtained University of Hawaii adaptive optics images of UY Aur and GG Tau resolve circumbinary disks in both systems. We apply our method to the intensity distributions revealed by the images to constrain the particle size distributions and densities for both systems. We obtain good fits to both the extinction profile and the observed intensity variations on the front and back side of the disk with a rather steep (\sim-4.7) power law distribution and a range of dust sizes ranging from 0.03 and 0.6 microns. A significant population of grains larger than 0.6 microns is not supported by the observations.

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