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Linear polarization of radio frequency lines in molecular clouds and circumstellar envelopes

Goldreich, Peter and Kylafis, Nikolaos D. (1982) Linear polarization of radio frequency lines in molecular clouds and circumstellar envelopes. Astrophysical Journal, 253 (1). pp. 606-621. ISSN 0004-637X. doi:10.1086/159663.

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We predict that interstellar lines possess a few percent linear polarization provided that the optical depth in the source region is both anisotropic and of order unity and the radiative rates are at least comparable to the collision rates. These conditions are expected to be met in many sources which emit radio and far-infrared line radiation. Under circumstances in which the Zeeman splitting exceeds both the radiative and collisional rates the linear polarization is aligned either parallel or perpendicular to the projection of the magnetic field on the plane of the sky. This "strong magnetic field" limit is expected to apply to all radio frequency lines and to many of those far infrared lines which form between levels whose magnetic moments are comparable to the Bohr magneton. The "weak magnetic field" limit is relevant to most far-infrared lines formed between levels with magnetic moments of order the nuclear magneton. In this limit the polarization direction is determined by the orientation of the propagation direction with respect to the anisotropic optical depth.

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Additional Information:© 1982 American Astronomical Society. Received 1981 April 27; accepted 1981 August 18. We are indebted to Charles Alcock, Fred Lo, and Tom Phillips for helpful advice. This research was supported by NSF grants AST80-20005 and AST79-22012. This is contribution number 3613 from the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
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Subject Keywords:interstellar: molecules, polarization, radio sources: linesstars: circumstellar shells, Zeeman effect
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Caltech Division of Geological and Planetary Sciences3613
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Official Citation:Linear polarization of radio frequency lines in molecular clouds and circumstellar envelopes Goldreich, P. & Kylafis, N. D Astrophysical Journal, Part 1, vol. 253, Feb. 15, 1982, p. 606-621.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37368
Deposited By: Ruth Sustaita
Deposited On:07 Mar 2013 19:34
Last Modified:09 Nov 2021 23:28

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