VLBA Observations of G5.89-0.39: OH masers and magnetic field structure

Abstract

We present VLBA observations of 1667 MHz OH maser emission from the massive star formation region G5.89-0.39. The observations were phase referenced allowing the absolute positions of the masers to be obtained. The 1667 MHz masers have radial velocities that span ~50 km/s but show little evidence of tracing the bipolar molecular outflow, as has been claimed in previous studies. We identify 23 Zeeman pairs through comparison of masers in left and right circular polarization. Magnetic field strengths range from -2 mG to +2 mG, and an ordered reversal in magnetic field direction is observed toward the southern region of the UC HII region. We suggest that the velocity and magnetic field structure of the 1667 MHz masers can be explained in the context of a model in which the masers arise in a neutral shell just outside a rapidly exanding ionized shell.

arXiv comment32 pages, 12 figures, accepted for publication in ApJ

References in corpus (5)

• The Physical Conditions for Massive Star Formation: Dust Continuum Maps and Modeling
• New OH Zeeman measurements of magnetic field strengths in molecular clouds
• Full-Polarization Observations of OH Masers in Massive Star-Forming Regions: I. Data
• Full-Polarization Observations of OH Masers in Massive Star-Forming Regions: II. Maser Properties and the Interpretation of Polarization
• Mapping the Outflow from G5.89-0.39 in SiO(5-4)

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• The 6-GHz methanol multibeam maser catalogue I: Galactic Centre region, longitudes 345 to 6
• Subarcsecond Submillimeter Imaging of the Ultracompact HII Region G5.89-0.39
• Evolution of Magnetic Fields in High Mass Star Formation: SMA dust polarization image of the UCHII region G5.89-0.39
• Water masers accompanying OH and methanol masers in star formation regions
• Magnetic Fields in Massive Star-Forming Regions (MagMaR) I. Linear Polarized Imaging of the UCHII Region G5.89-0.39
• New Distance and Revised Natures of High Mass Star Formation in G5.89-0.39
• Parkes full polarization spectra of OH masers - I. Galactic longitudes 350 through the Galactic Centre to 41
• CO J=1-0 observations of molecular gas interacting with galactic supernova remnants G5.4-1.2, G5.55+0.32 and G5.71-0.08
• Masers and star formation