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Magnetic Fields in Molecular Cloud Cores

Published online by Cambridge University Press:  19 July 2016

Z.P. Zhou  and
X.W. Zheng
Z.P. Zhou
Affiliation:
1Division of Radioastronomy, Purple Mountain Observatory, Nanjing, China
X.W. Zheng
Affiliation:
2Department of Astronomy, Nanjing University, Nanjing, China

Extract

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Strong circular polarization of OH masers at 1665 and 1667 MHz lines has been observed towards the molecular cloud cores associated with HII regions. Magnetic field strengths of a few mG are derived from the Zeeman splitting of OH lines. For instance, a magnetic field of about 4 mG in the masing region of W3(OH) has been estimated by OH-line Zeeman splitting (Davies, 1974). VLBI observations show that the OH maser spots project onto or very close to the surface of associated compact HII regions (Reid et al., 1986). The observational evidence demonstrates that the scales of OH maser components surrounding a compact HII region (R ~ 1016 cm) are about 1014 cm in diameter with an amplification pathlength of ~1015 cm. Hence the magnetic fields determined by the Zeeman splitting of OH maser lines appear partly very close to the associated HII region. Elitzur (1979) has theoretically obtained similar results as above.

Type
6. Magnetic Fields in Molecular Clouds, Dark Globules and in the Pre-Stellar and Circumstellar Environment
Information
Symposium - International Astronomical Union , Volume 140: Galactic and Intergalactic Magnetic Fields , 1990 , pp. 291 - 292
Copyright
Copyright © Kluwer 1990 

References

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