AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 99. The ISM: Structure, Composition and Star Formation
Oral, Thursday, June 3, 1999, 2:00-3:30pm, International Ballroom South

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[99.06] Measurement of Magnetic Fields from Linear Polarization of Dust Emission

R. Rao, R.M. Crutcher (U. of Illinois, Urbana-Champaign)

The goal of the thesis was to be able to study the role of magnetic fields in the star formation process. The direction of the plane of sky component of the magnetic field can be obtained by mapping the linear polarization of dust emission from aligned dust grains. In order to achieve the stated objective, we designed and built a polarimetry system for the ten-element Berkeley Illinois Maryland Association (BIMA) array. The polarimetry systems were designed to work at 90 GHz (3.3 mm) and 230 GHz (1.3 mm).

One of the prime objects that was chosen for this study was the star forming region in Orion BN/KL. Previous polarimetric studies with lower resolution have shown that the polarization direction (and the field) is uniform across the cloud but with a decrease in the degree of polarization towards BN/KL. The BIMA observations, which have a resolution of approximately 4\arcsec, show that this decrease in polarization is due to considerable structure in the polarization vectors. However, it must be pointed out that this structure in the polarization does not necessarily imply that the field is twisted. It is possible that alternative grain alignment mechanisms might cause this observed change in the polarization and that the field is relatively uniform.

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