EVOLUTION OF MAGNETIC FIELDS IN HIGH MASS STAR FORMATION: SUBMILLIMETER ARRAY DUST POLARIZATION IMAGE OF THE ULTRACOMPACT H II REGION G5.89-0.39
- Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan (China)
- Academia Sinica Institute of Astronomy and Astrophysics, P. B. Box 23-141, Taipei 10617, Taiwan (China)
- Institut de Ciencies de l' Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, Torre C5-parell 2, 08193 Bellaterra, Catalunya (Spain)
We report high angular resolution (3'') Submillimeter Array (SMA) observations of the molecular cloud associated with the Ultracompact H II region G5.89 - 0.39. Imaged dust continuum emission at 870 {mu}m reveals significant linear polarization. The position angles (P.A.s) of the polarization vary enormously but smoothly in a region of 2 x 10{sup 4} AU. Based on the distribution of the P.A.s and the associated structures, the polarized emission can be separated roughly into two components. The component 'x' is associated with a well-defined dust ridge at 870 {mu}m, and is likely tracing a compressed B field. The component 'o' is located at the periphery of the dust ridge and is probably from the original B field associated with a pre-existing extended structure. The global B field morphology in G5.89, as inferred from the P.A.s, is clearly disturbed by the expansion of the H II region and the molecular outflows. Using the Chandrasekhar-Fermi method, we estimate from the smoothness of the field structures that the B field strength in the plane of sky can be no more than 2-3 mG. We then compare the energy densities in the radiation, the B field, and the mechanical motions as deduced from the C{sup 17}O 3-2 line emission. We conclude that the B field structures are already overwhelmed and dominated by the radiation, outflows, and turbulence from the newly formed massive stars.
- OSTI ID:
- 21296243
- Journal Information:
- Astrophysical Journal, Vol. 695, Issue 2; Other Information: DOI: 10.1088/0004-637X/695/2/1399; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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