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Quantum-Chemical calculations revealing the effects of magnetic fields on methanol masers

Published online by Cambridge University Press:  16 July 2018

Boy Lankhaar ,
Wouter Vlemmings ,
Gabriele Surcis ,
Huib Jan van Langevelde ,
Gerrit C. Groenenboom  and
Ad van der Avoird
Boy Lankhaar
Affiliation:
Department of Space, Earth and Envoirment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden email: [email protected]
Wouter Vlemmings
Affiliation:
Department of Space, Earth and Envoirment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
Gabriele Surcis
Affiliation:
INAF-Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius, Italy
Huib Jan van Langevelde
Affiliation:
Joint Institute for VLBI ERIC, Postbus 2, 7990 AA Dwingeloo, The Netherlands Sterrewacht Leiden, Leiden University, 9513, 2330 RA Leiden, the Netherlands
Gerrit C. Groenenboom
Affiliation:
Theoretical Chemistry, Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
Ad van der Avoird
Affiliation:
Theoretical Chemistry, Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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Abstract

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Maser observations of both linearly and circularly polarized emission have provided unique information on the magnetic field in the densest parts of star forming regions, where non-maser magnetic field tracers are scarce. While linear polarization observations provide morphological constraints, magnetic field strengths are determined by measuring the Zeeman splitting in circularly polarized emission. Methanol is of special interest as it is one of the most abundant maser species and its different transitions probe unique areas around the protostar. However, its precise Zeeman-parameters are unknown. Experimental efforts to determine these Zeeman-parameters have failed. Here we present quantum-chemical calculations of the Zeeman-parameters of methanol, along with calculations of the hyperfine structure that are necessary to interpret the Zeeman effect in methanol. We use this model in re-analyzing methanol maser polarization observations. We discuss different mechanisms for hyperfine-state preference in the pumping of torsion-rotation transitions involved in the maser-action.

Keywords

magnetic fieldsmasersmolecular datapolarization
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 13 , Symposium S336: Astrophysical Masers: Unlocking the Mysteries of the Universe , September 2017 , pp. 23 - 26
Copyright
Copyright © International Astronomical Union 2018 

References

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