A Caltech Library Service

Non-Zeeman Circular Polarization of Molecular Rotational Spectral Lines

Houde, Martin and Hezareh, Talayeh and Jones, Scott and Rajabi, Fereshte (2013) Non-Zeeman Circular Polarization of Molecular Rotational Spectral Lines. Astrophysical Journal, 764 (1). Art. No. 24. ISSN 0004-637X.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


We present measurements of circular polarization from rotational spectral lines of molecular species in Orion KL, most notably ^(12)CO (J = 2 → 1), obtained at the Caltech Submillimeter Observatory with the Four-Stokes-Parameter Spectral Line Polarimeter. We find levels of polarization of up to 1%-2% in general; for ^(12)CO (J = 2 → 1) this level is comparable to that of linear polarization also measured for that line. We present a physical model based on resonant scattering in an attempt to explain our observations. We discuss how slight differences in scattering amplitudes for radiation polarized parallel and perpendicular to the ambient magnetic field, responsible for the alignment of the scattering molecules, can lead to the observed circular polarization. We also show that the effect is proportional to the square of the magnitude of the plane of the sky component of the magnetic field and therefore opens up the possibility of measuring this parameter from circular polarization measurements of Zeeman insensitive molecules.

Item Type:Article
Related URLs:
URLURL TypeDescription
Additional Information:© 2013 American Astronomical Society. Received 2012 August 19; accepted 2012 December 10; published 2013 January 21. M.H. is grateful to C. Cohen-Tannoudji of the Ecole Normale Sup´erieure de Paris for an insightful discussion. M.H.’s research is funded through the NSERC Discovery Grant, Canada Research Chair, and Western’s Academic Development Fund programs. T.H. is funded by the Alexander von Humboldt foundation in Germany. The Caltech Submillimeter Observatory is operated by the California Institute of Technology under cooperative agreement with the National Science Foundation (AST-0838261).
Funding AgencyGrant Number
Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery GrantUNSPECIFIED
Canada Research ChairUNSPECIFIED
Western’s Academic Development Fund programsUNSPECIFIED
Alexander von Humboldt FoundationUNSPECIFIED
Subject Keywords:ISM: clouds; ISM: individual objects (Orion KL); ISM: magnetic fields; ISM: molecules; polarization
Issue or Number:1
Record Number:CaltechAUTHORS:20130312-085254762
Persistent URL:
Official Citation:Non-Zeeman Circular Polarization of Molecular Rotational Spectral Lines Martin Houde et al. 2013 ApJ 764 24
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37457
Deposited By: Ruth Sustaita
Deposited On:12 Mar 2013 16:39
Last Modified:03 Oct 2019 04:47

Repository Staff Only: item control page