EVN observations of 6.7-GHz methanol maser polarization in massive star-forming regions II. First statistical results

Abstract

Magnetic fields have only recently been included in theoretical simulations of high-mass star formation. The simulations show that magnetic fields play an important role in the formation and dynamics of molecular outflows. Masers, in particular 6.7-GHz CH3OH masers, are the best probes of the magnetic field morphologies around massive young stellar objects on the smallest scales of 10-100 AU. This paper focuses on 4 massive young stellar objects, IRAS06058+2138-NIRS1, IRAS22272+6358A, S255-IR, and S231, which complement our previous 2012 sample (the first EVN group). From all these sources, molecular outflows have been detected in the past. Seven of the European VLBI Network antennas were used to measure the linear polarization and Zeeman-splitting of the 6.7-GHz CH3OH masers in the star-forming regions in this second EVN group. We detected a total of 128 CH3OH masing cloudlets. Fractional linear polarization (0.8%-11.3%) was detected towards 18% of the CH3OH masers in our sample. The linear polarization vectors are well ordered in all the massive young stellar objects. We measured significant Zeeman-splitting in IRAS06058+2138-NIRS1 (DVz=3.8+/-0.6 m/s) and S255-IR (DVz=3.2+/-0.7 m/s). By considering the 20 massive young stellar objects towards which the morphology of magnetic fields was determined by observing 6.7-GHz CH3OH masers in both hemispheres, we find no evident correlation between the linear distributions of CH3OH masers and the outflows or the linear polarization vectors. On the other hand, we present first statistical evidence that the magnetic field (on scales 10-100 AU) is primarily oriented along the large-scale outflow direction. Moreover, we empirically find that the linear polarization fraction of unsaturated CH3OH masers is P_l<4.5%.

13 pages, 8 figures, 7 tables, accepted by Astronomy & Astrophysics

References in corpus (6)

• Theory of Star Formation
• Interferometric multi-wavelength (sub)millimeter continuum study of the young high-mass protocluster IRAS05358+3543
• A new probe of magnetic fields during high-mass star formation: Zeeman splitting of 6.7 GHz methanol masers
• The Ionization of Accretion Flows in High Mass Star Formation: W51e2
• Associations of water and methanol masers at milli-arcsec angular resolution in two high-mass young stellar objects
• Who Is Eating the Outflow?: High-Angular Resolution Study of an Intermediate-Mass Protostar in L1206

Cited by in corpus (15)

• Review of Zeeman Effect Observations of Regions of Star Formation
• Giant burst of methanol maser in S255IR-NIRS3
• A multiple system of high-mass YSOs surrounded by disks in NGC7538 IRS1
• Velocity and magnetic fields within 1000 AU from a massive YSO
• Protostellar Outflows at the EarliesT Stages (POETS). II. A possible radio synchrotron jet associated with the EGO G035.02+0.35
• A Galactic survey of radio jets from massive protostars
• EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions III. The flux-limited sample
• Linear Polarization of Class I Methanol Masers in Massive Star-Forming Regions
• 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
• The magnetic field at milliarcsecond resolution around IRAS20126+4104
• Simulated Galactic methanol maser distribution to constrain Milky Way parameters
• EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions. V. Completion of the flux-limited sample
• OH maser toward IRAS 06056+2131: polarization parameters and evolution status
• Polarization properties of methanol masers
• Physical conditions around high-mass young star-forming objects via simultaneous observations of excited OH and methanol masers