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Non-Zeeman circular polarization of CO rotational lines in SNR IC 443

Hezareh, Talayeh and Wiesemeyer, Helmut and Houde, Martin and Gusdorf, Antoine and Siringo, Giorgio (2013) Non-Zeeman circular polarization of CO rotational lines in SNR IC 443. Astronomy and Astrophysics, 558 . Art. No. A45. ISSN 0004-6361.

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Context. We study interstellar magnetic fields by measuring the polarization in molecular spectral lines and thermal emission of dust. Aims. We report detection of non-Zeeman circular polarization and linear polarization levels of up to 1% in the ^(12)CO spectral line emission in a shocked molecular clump around the supernova remnant (SNR) IC 443. We examine our polarization results to confirm that the circular polarization signal in CO lines is caused by a conversion of linear to circular polarization, consistent with anisotropic resonant scattering. In this process background, linearly polarized CO emission interacts with similar foreground molecules aligned with the ambient magnetic field and scatters at a transition frequency. The difference in phase shift between the orthogonally polarized components of this scattered emission can cause a transformation of linear to circular polarization. Methods. We compared linear polarization maps from the dust continuum, which were obtained with PolKa at APEX, and ^(12)CO (J = 2 → 1) and (J = 1 → 0) from the IRAM 30-m telescope. We found no consistency between the two sets of polarization maps. We then reinserted the measured circular polarization signal in the CO lines across the source to the corresponding linear polarization signal to test whether the linear polarization vectors of the CO maps were aligned with those of the dust before this linear to circular polarization conversion. Results. After the flux correction for the two transitions of the CO spectral lines, the new polarization vectors for both CO transitions aligned with the dust polarization vectors, establishing that the non-Zeeman CO circular polarization is due to a linear to circular polarization conversion.

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Additional Information:© 2013 ESO. Article published by EDP Sciences. Received 15 May 2013. Accepted 8 August 2013. Published online 01 October 2013. The authors are grateful to C. Thum for very helpful and constructive comments and discussion. T. Hezareh’s research was funded by the Alexander von Humboldt foundation. M. Houde’s research is funded through the NSERC Discovery Grant, Canada Research Chair, Canada Foundation for Innovation, and Western’s Academic Development Fund programs. A. Gusdorf acknowledges support by the grant ANR-09-BLAN-0231-01 from the French Agence Nationale de la Recherche as part of the SCHISM project.
Funding AgencyGrant Number
Alexander von Humboldt foundationUNSPECIFIED
Canada Research ChairUNSPECIFIED
Canada Foundation for InnovationUNSPECIFIED
Western’s Academic Development Fund programsUNSPECIFIED
Agence Nationale de la Recherche (ANR) SCHISM ProjectANR-09-BLAN-0231-01
Subject Keywords:polarization – techniques: spectroscopic – ISM: magnetic fields – ISM: clouds – ISM: individual objects: IC 443
Record Number:CaltechAUTHORS:20140108-130917649
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Official Citation:Non-Zeeman circular polarization of CO rotational lines in SNR IC 443 Talayeh Hezareh, Helmut Wiesemeyer, Martin Houde, Antoine Gusdorf and Giorgio Siringo A&A 558 A45 (2013) DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43269
Deposited By: Ruth Sustaita
Deposited On:08 Jan 2014 21:30
Last Modified:03 Oct 2019 06:06

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