Magnetic field structure in the bipolar outflow source G 35.2-0.74N: MERLIN spectral line results

MERLIN polarization measurements of the OH 1665-MHz maser emission from the bipolar outflow source G 35.2-0.74N are presented. The masers have an elongated distribution, and a velocity gradient which is interpreted in terms of a disc surrounding the source of the outflow. The radius of the maser disc is 1.3 arcsec (2600 au at 2 kpc). Analysis of the OH maser polarization reveals four Zeeman pairs, with field strengths ranging from -2.5 to +5.3 mG. The direction of the field reverses on opposite sides of the disc. Linear polarization is found in five of the masers, and is used to infer the three-dimensional magnetic field direction at these points. The data lend support to the hydromagnetic model proposed by Uchida & Shibata.