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Session 121 - Molecular Clouds/Star Formation.
Oral session, Saturday, January 10
Georgetown,
This paper presents large scale polarization maps (8' \times 8') of the Orion molecular cloud (OMC-1) at far-infrared (100 \mum; 35'' resolution) and submillimeter (350 \mum; 18'' resolution) wavelengths. The magnetic field shows a pinch at scales less than 1/2 pc with a centroid that is on the OMC-1 ridge, a site of high mass star formation. We infer that gravitational collapse pulled the magnetic field into an hourglass shape. We estimate that the magnetic, kinetic, and gravitational energies are in equipartition on the ridge and that the magnetic energy dominates in the surrounding ambient envelope. We consider a model in which the ridge and thus high mass stars gravitationally collapsed out of a cloud that was initially supported by the magnetic field. At flux peaks there is a reduction in the percent polarization. This effect is discussed in relation to temperature, optical depth, and wavelength.
