EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions. V. Completion of the flux-limited sample

Abstract

Although the role of magnetic fields in launching molecular outflows in massive YSOs has been convincingly demonstrated by theoretical arguments, observationally, the alignment of the magnetic field lines with the molecular outflows is still under debate. We aim to complete the measurements of the direction of the magnetic fields at mas resolution around a sample of massive star-forming regions (MSFRs) to determine whether the magnetic field and outflows are aligned. In 2012, we started a large VLBI campaign with the EVN to measure the magnetic field orientation and strength toward a sample of 31 MSFRs (the flux-limited sample) by analyzing the polarized emission of 6.7GHz CH3OH masers. In the previous papers of the series, we have presented 80% of the sample. Here, we report the linearly and circularly polarized emission of 6.7GHz CH3OH masers toward the last five MSFRs of the flux-limited sample. The sources are G30.70-0.07, G30.76-0.05, G31.28+0.06, G32.03+0.06, and G69.52-0.97. We detected a total of 209 masers, 15% of which show linearly polarized emission (0.07%-16.7%), and 2% of which show circularly polarized emission (0.2%-4.2%). Zeeman splitting was measured toward G30.70-0.07, G32.03+0.06, and G69.52-0.97. The statistical analysis of the entire flux-limited sample shows that the observations are consistent with a bimodal distribution in the difference between the 3D magnetic field direction and the outflow axis, with half the magnetic field directions being perpendicular and the other half being parallel to the outflow. In addition, we determined that typical values of the linear and circular polarization fractions for 6.7 GHz CH3OH masers are Pl=1.0%-2.5% and Pv=0.5%-0.75%, respectively. We found that a typical Zeeman splitting is in the range between 0.5 m/s and 2.0 m/s. This would correspond to 9 mG<$|B_{||}|$<40 mG if F=3->4 is the most favored hyperfine transition.

22 pages, 12 figures, 9 tables, accepted by Astronomy & Astrophysics. arXiv admin note: text overlap with arXiv:1902.08210

References in corpus (19)

• Magnetic Fields and Massive Star Formation
• The SFXC software correlator for Very Long Baseline Interferometry: Algorithms and Implementation
• Interferometric observations of magnetic fields in forming stars
• A SCUBA imaging survey of ultracompact HII regions: The environments of massive star formation
• The Role of Magnetic Fields in Protostellar Outflows and Star Formation
• Trigonometric Parallaxes of Star Forming Regions in the Scutum Spiral Arm
• A new probe of magnetic fields during high-mass star formation: Zeeman splitting of 6.7 GHz methanol masers
• Review of Zeeman Effect Observations of Regions of Star Formation
• The Role of Outflows, Radiation Pressure, and Magnetic Fields in Massive Star Formation
• Discovery of six new class II methanol maser transitions, including the unambiguous detection of three torsionally excited lines toward G358.931-0.030
• Massive Outflows Driven by Magnetic Effects II: Comparison with Observations
• EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions III. The flux-limited sample
• Proper Motions of OH Masers and Magnetic Fields in Massive Star-Forming Regions
• Rapidly increasing collimation and magnetic field changes of a H2O maser outflow
• Enhanced density and magnetic fields in interstellar OH masers
• A MERLIN Study of 6 GHz Excited-state OH & 6.7 GHz Methanol Masers in ON1
• EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions IV. Magnetic field strength limits and structure for 7 additional sources
• Methanol masers reveal the magnetic field of the high-mass protostar IRAS 18089-1732
• Star formation in IRDC G31.97+0.07

Cited by in corpus (4)

• Monitoring of the polarized $H_{2}O$ maser emission around the massive protostars W75N(B)-VLA1 and W75N(B)-VLA2
• Inverse MultiView II: Microarcsecond Trigonometric Parallaxes for Southern Hemisphere 6.7~GHz Methanol Masers G232.62+00.99 and G323.74$-$00.26
• The magnetic field of a magnetohydrodynamic disk wind: Water maser observations and simulations
• Physical conditions around high-mass young star-forming objects via simultaneous observations of excited OH and methanol masers