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[114.03] The Patchiness of Galactic Dust

P. Popowski (MPA, Garching)

I consider a disk of discrete dust clouds as a model of dust distribution in the Milky Way. In this formulation, "a cloud" is a dust unit that acts as a uniform screen of extinction over its angular extent. Extinction maps provide interesting constraints for such a model. I discuss two limiting cases of cloud populations with very large and very small sizes in relation to the resolution element of an extinction map. Large clouds produce uniform extinction over the entire resolution element, the small ones result in patchy extinction. I analyze the color-magnitude diagrams collected by the MACHO microlensing survey in the Galactic bulge and used by Popowski, Cook, and Becker (2003) to construct a large-scale extinction map. The relation between the mean and variance of stellar colors in those color-magnitude diagrams indicates that the dust is patchy on angular scales of a few arc-minutes or less. This suggests that the dust clouds are likely smaller than one parsec across.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.