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[16.12] Constraining Cometary Particle Size Distributions by Combining Dynamic and Thermal Emission Models

M. S. Kelley, C. E. Woodward, R. D. Gehrz (U. Minn.), D. E. Haker (UCSD), W. T. Reach (SSC/Caltech), D. H. Wooden (NASA Ames)

We present a model for cometary coma structures that utilizes grain mineralogy as a basis for determining the dust grain "\beta," the ratio of solar radiation pressure to gravity, a parameter inversely proportional to particle size. Generally in models of comae structures, the \beta distribution, dn/d\beta, is an input parameter constrained by fitting coma morphologies to observations. Here, dn/d\beta refers to particles released by the nucleus. In this model, we additionally constrain \beta by fitting the thermal spectral energy distribution with a size distribution of porous siliceous mineral grains and amorphous carbon grains, modeled for an observed aperture on the sky. Both thermal emission and dynamic models have worthy assumptions, but the combination of the two independent methods narrows the allowed parameter space for a more robust constraint on the grain size distribution. We present our efforts to combine a mid-infrared model and dynamic model of comet 2P/Encke as observed by the Spitzer Space Telescope in June 2004.

This work partially supported by the National Science Foundation grant AST-037446.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.