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Paper: Circular Polarization Mapping of Protostellar Environments: Searching for Aligned Grains
Volume: 343, Astronomical Polarimetry: Current Status and Future Directions
Page: 122
Authors: Clayton, G.C.; Whitney, B.A.; Wolff, M.J.; Smith, P.; Gordon, K.D.
Abstract: We have mapped the linear and circular polarization in several protostars. The polarization maps are being compared to Monte Carlo radiative transfer models including the effects of scattering from aligned grains. A definitive test of grain alignment comes from resolved circular polarization maps of protostars. Aligned grains produce large values of circular polarization across the cloud, up to 25-40% in the models, whereas nonaligned grains produce maximum polarizations of only a few percent. To date, very few protostars have been observed at high spatial resolution for circular polarization. If grains are aligned, models of the linear and circular polarization maps can probe the alignment geometry and therefore the magnetic field structure. None of the four protostars observed showed circular polarization at a level above ∼ 1-2 % (3σ).
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