EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions III. The flux-limited sample

Abstract

Theoretical simulations and observations at different angular resolutions have shown that magnetic fields have a central role in massive star formation. Like in low-mass star formation, the magnetic field in massive young stellar objects can either be oriented along the outflow axis or randomly. Measuring the magnetic field at milliarcsecond resolution (10-100 au) around a substantial number of massive young stellar objects permits determining with a high statistical significance whether the direction of the magnetic field is correlated with the orientation of the outflow axis or not. In late 2012, we started a large VLBI campaign with the European VLBI Network to measure the linearly and circularly polarized emission of 6.7 GHz methanol masers around a sample of massive star-forming regions. This paper focuses on the first seven observed sources, G24.78+0.08, G25.65+1.05, G29.86-0.04, G35.03+0.35, G37.43+1.51, G174.20-0.08, and G213.70-12.6. For all these sources, molecular outflows have been detected in the past. We detected a total of 176 methanol masing cloudlets toward the seven massive star-forming regions, 19% of which show linearly polarized emission. The methanol masers around the massive young stellar object MM1 in G174.20-0.08 show neither linearly nor circularly polarized emission. The linear polarization vectors are well ordered in all the other massive young stellar objects. We measured significant Zeeman splitting toward both A1 and A2 in G24.78+0.08, and toward G29.86-0.04 and G213.70-12.6. By considering all the 19 massive young stellar objects reported in the literature for which both the orientation of the magnetic field at milliarcsecond resolution and the orientation of outflow axes are known, we find evidence that the magnetic field (on scales 10-100 au) is preferentially oriented along the outflow axes.

arXiv comment17 pages, 10 figures, 9 tables, accepted by Astronomy & Astrophysics. arXiv admin note: text overlap with arXiv:1306.6335

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• Review of Zeeman Effect Observations of Regions of Star Formation
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• VLA Survey of Dense Gas in Extended Green Objects: Prevalence of 25 GHz Methanol Masers
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• Superflares of H${}_2$O Maser Emission in the Protostellar Object IRAS 18316$-$0602
• Methanol masers reveal the magnetic field of the high-mass protostar IRAS 18089-1732
• JVLA overview of the bursting H${}_2$O maser source G25.65+1.05
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• EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions. V. Completion of the flux-limited sample
• The magnetic field of a magnetohydrodynamic disk wind: Water maser observations and simulations
• Polarized Maser Emission with In-Source Faraday Rotation
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• Physical conditions around high-mass young star-forming objects via simultaneous observations of excited OH and methanol masers
• First detection of circular polarization in 4.7 GHz excited OH masers