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H. Li, G. S. Griffin, M. Krejny, G. Novak (Northwestern University), R. F. Loewenstein, M. G. Newcomb (University of Chicago), P. G. Calisse (Cardiff University, Wales, U.K.), D. T. Chuss (NASA - Goddard Space Flight Center)
The formation of Giant Molecular Clouds (GMCs) is a poorly understood step in the star formation process. Magentic fields may play a role in GMC formation. We report the results of an observational study of magnetic fields in GMCs and in the less dense interstellar regions that surround them.
SPARO (Submillimeter Polarimeter for Antarctic Remote Observations) is an instrument designed to measure 450 micron polarization using the two-meter Viper telescope located at South Pole station. It obtains excellent sensitivity to large-scale polarized emission. Using SPARO, we measured projected magnetic field directions in four GMCs: NGC6334, Carina, G333.6-0.2, and G331.5-0.1. There is a clearly defined mean field direction for each cloud.
To obtain the magnetic field directions in the less dense regions, we used Heiles' optical "Stellar polarization catalogs agglomeration" (Astron. J., 2000). We estimated the mean field directions for about a dozen regions, each about 300pc in extent, including two that are centered near NGC6334 and Carina. For those two clouds, we find agreement between the field direction revealed by optical polarimetry and that measured using SPARO. The other two GMCs are too far to be studied using the Heiles catalog.
Our results suggest that the physical processes leading to the formation of GMCs preserve the mean field direction. This work was supported by the National Science Foundation's Office of Polar Programs.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.