AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 69. The Young Ones 2: T-Tauri Stars, H-H Objects and Modeling
Display, Wednesday, June 2, 1999, 10:00am-6:30pm, Southwest Exhibit Hall

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[69.03] Dust Grain Populations in T~Tauri Environments

T.L. Huard, D.A. Weintraub (Vanderbilt Univ.)

Previous Monte Carlo modeling of the near-infrared polarization and intensity maps of T~Tauri environments have primarily incorporated the optical properties of standard Mathis, Rumpl, & Nordsieck (MRN; 1977, ApJ, 217, 425) interstellar dust grains. The MRN population includes grains with radii from 0.05~\mum -- 0.25~\mum. More recently, Kim, Martin,& Hendry (1994, ApJ, 422, 164) have developed a revised interstellar grain population which includes slightly larger grains. However, neither MRN nor KMH interstellar grain populations are applicable to environments surrounding T~Tauri stars.

Submillimeter and millimeter observations of T~Tauri environments imply dust opacities consistent with a circumstellar dust population having a larger mean radius than that of the MRN or KMH interstellar grains. In fact, these observations are consistent with the presence of millimeter-sized grains, implying that significant grain growth has occurred.

We have developed grain distributions that include very large grains such as those suggested by the submillimeter observations. We compare the near-infrared polarization and intensity signatures observed in scattering nebulae surrounding T~Tauri stars with those produced in our Monte Carlo simulations which include the large grain populations.

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