Circular polarization of astrophysical masers due to overlap of Zeeman components

TLDR: In this paper, the polarization due to the overlap of Zeeman components that arises in the radiation from astrophysical masers was investigated and the essential simplicity of this previously unrecognized effect is a compelling argument in its favor as the basic cause for the strong, net circular polarization of the OH masers.

Abstract: Calculational methods are presented and utilized in an idealized case to evaluate the polarization due to the overlap of Zeeman components that arises in the radiation from astrophysical masers. The essential simplicity of this previously unrecognized effect is a compelling argument in its favor as the basic cause for the strong, net circular polarization of the OH masers. Observations can then be interpreted to yield an estimate for the strength of the magnetic fields in the masing regions, even when Zeeman pairs cannot be identified as is usually the situation. Magnetic fields of approximately a milligauss or greater are inferred to be common in the masing gas associated with regions of star formation. This estimate should be considerably more general than the specific assumptions of our calculation.