Magnetic field structure of the star-forming region W3(OH) - VLBI spectral line results

The authors have conducted a six-station, VLBI observation of the ground state 1665 MHz OH emission source in W3(OH) with full polarization information. They have been able (1) to produce spectral line VLBI synthesis maps in all Stokes parameters; (2) to identify several Zeeman pairs; (3) to determine the percent of linear, circular, and total polarization of the emission of each feature; and (4) to infer some information about the three-dimensional structure of the magnetic field. Eighty-one maser components stronger than 1.5 Jy were detected. Sixty-five exhibited pure circular polarization. These observations suggest that the OH cloud is permeated with a magentic field having an average strength of 6 mG.