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Radiative Alignment Torque Modeling

Presentation #232.05 in the session “Molecular Clouds”.

Published onJun 18, 2021
Radiative Alignment Torque Modeling

Interstellar polarization was first discovered over 70 years ago, yet the underlying physical mechanisms that cause the observed polarization were not well understood for decades. Recent developments in a quantitative description of Radiative Alignment Torque (RAT) theory affirms it as the most promising mechanism to explain interstellar polarization through dust grain alignment. This research seeks to understand and explore the physical significance and limitations of RAT theory and its theoretical polarization models by probing a diverse parameter space. We first explored the general use of the “Serkowski Law” with well-documented polarization data to confirm the suitability of Serkowski modeling. We then obtained quantitative insight into the source of dust grain alignment by applying Sekowski models to theoretical polarization as outlined in RAT theory. Polarization observations towards the Taurus Molecular Cloud show a sharp increase in peak polarization wavelength in some regions of large extinction. The implied grain growth is found to be caused by accelerated grain coagulation in regions of higher density and ice formation on the grain surface in regions of higher extinction. We conclude that the polarization trends of the Taurus Molecular Cloud may be explained by grain growth among aligned dust grains. Future work will entail verifying modeling accuracy of the Taurus Molecular Cloud, identifying unique solutions, and probing the limitations of the parameter space.

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