Non-Zeeman Circular Polarization of Molecular Maser Spectral Lines

Abstract

We apply the anisotropic resonant scattering model developed to explain the presence of non-Zeeman circular polarization signals recently detected in the ${}^{12}\mathrm{CO}\left(J=2\to 1\right)$ and $\left(J=1\to 0\right)$ transitions in molecular clouds to Stokes $V$ spectra of SiO $v=1$ and $v=2$, $\left(J=1\to 0\right)$ masers commonly observed in evolved stars. It is found that the observed antisymmetric "S" and symmetric "$\cup$" or "$\cap$" shaped spectral profiles naturally arise when the maser radiation scatters off populations of foreground molecules located outside the velocity range covered by the background maser radiation. Using typical values for the relevant physical parameters, it is estimated that magnetic field strengths on the order of a few times 15 mG are sufficient to explain the observational results found in the literature.

arXiv commentApJ Accepted. 19 pages, 4 figures

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Cited by in corpus (13)

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• The Zeeman Effect in the 44 GHz Class I Methanol Maser Line toward DR21(OH)
• Characterizing maser polarization: effects of saturation, anisotropic pumping and hyperfine structure
• Simultaneous VLBA polarimetric observations of the v=$\{$1,2$\}$ J=1-0 and v=1, J=2-1 SiO maser emission toward VY CMa II: component-level polarization analysis
• Magnetic Field Structure of Orion Source I
• Non-Zeeman Circular Polarization of Molecular Spectral Lines in the ISM
• The generation and transformation of polarisation signals in molecular lines through collective anisotropic resonant scattering
• The Zeeman Effect in the 44 GHz Class I Methanol (CH3OH) Maser Line Toward DR21W
• Polarization properties of methanol masers
• SiO maser polarization and magnetic field in evolved cool stars
• A Curious Case of Circular Polarization in the 25 GHz Methanol Maser Line toward OMC-1