Characterization of methanol as a magnetic field tracer in star-forming regions
Journal article, 2018

Magnetic fields play an important role during star formation1. Direct magnetic field strength observations have proven particularly challenging in the extremely dynamic protostellar phase2,3,4. Because of their occurrence in the densest parts of star-forming regions, masers, through polarization observations, are the main source of magnetic field strength and morphology measurements around protostars2. Of all maser species, methanol is one of the strongest and most abundant tracers of gas around high-mass protostellar disks and in outflows. However, as experimental determination of the magnetic characteristics of methanol has remained largely unsuccessful5, a robust magnetic field strength analysis of these regions could hitherto not be performed. Here, we report a quantitative theoretical model of the magnetic properties of methanol, including the complicated hyperfine structure that results from its internal rotation6. We show that the large range in values of the Landé g factors of the hyperfine components of each maser line lead to conclusions that differ substantially from the current interpretation based on a single effective g factor. These conclusions are more consistent with other observations7,8 and confirm the presence of dynamically important magnetic fields around protostars. Additionally, our calculations show that (nonlinear) Zeeman effects must be taken into account to further enhance the accuracy of cosmological electron-to-proton mass ratio determinations using methanol9,10,11,12.




Zeeman effect

maser polarization


Boy Lankhaar

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Wouter Vlemmings

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

G. Surcis

Joint Institute for VLBI in Europe (JIVE)

H.J. van Langevelde

Joint Institute for VLBI in Europe (JIVE)

Gerrit C. Groenenboom

Radboud University

Ad van der Avoird

Radboud University

Nature Astronomy

23973366 (eISSN)

Vol. 2 145-150

Magnetic fields and the outflows during the formation and evolution of stars (OUTFLOWMAGN)

European Commission (EC) (EC/FP7/614264), 2014-05-01 -- 2019-04-30.

Fundamental physics, magnetic fields and gravity with recent and future radio interferometers

Swedish Research Council (VR) (2014-5713), 2014-01-01 -- 2019-12-31.

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences


Onsala Space Observatory



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