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Session 91 - Structure of Molecular Clouds.
Oral session, Wednesday, January 15
Images of the linearly polarized emission from magnetically aligned dust grains have been used to investigate the magnetic field structure in the dense environments of young stellar objects. These observations provide constraints for theoretical modeling on scales relevant to protostellar disks, envelopes and outflows. The high resolution polarimetric observations were obtained with the Owens Valley Radio Observatory Millimeter Array outfitted with adjustable reflecting polarizers. In particular, observations of the young stellar object NGC 1333/IRAS 4A are discussed. This object is highly embedded and the observed dust and gas may correspond to the magnetically supported envelopes predicted by theoretical models. Our polarization observations for IRAS 4A have resolved structure in the polarized dust emission. The magnetic field direction implied is parallel to the bipolar molecular outflow. Radiative transfer models were calculated and demonstrate that the structure in the polarized emission is consistent with an hourglass field morphology in the envelope. The detection of significant polarized emission in dense gas (n > 10^8 cm^-3) places constraints on grain alignment mechanisms.
Program listing for Wednesday