2011A&A...533A..47S

NGC7538 is a complex massive star-forming region. The region is composed of several radio continuum sources, one of which is IRS1, a high-mass protostar, from which a 0.3pc molecular bipolar outflow was detected. Several maser species have been detected around IRS1. The CH₃OH masers have been suggested to trace a Keplerian-disk, while the H₂O masers are almost aligned to the outflow. More recent results suggested that the region hosts a torus and potentially a disk, but with a different inclination than the Keplerian-disk that is supposed to be traced by the CH₃OH masers. Tracing the magnetic field close to protostars is fundamental for determining the orientation of the disk/torus. Recent studies showed that during the protostellar phase of high-mass star formation the magnetic field is oriented along the outflows and around or on the surfaces of the disk/torus. The observations of polarized maser emissions at milliarcsecond resolution can make a crucial contribution to understanding the orientation of the magnetic field and, consequently, the orientation of the disk/torus in NGC7538-IRS1. The NRAO Very Long Baseline Array was used to measure the linear polarization and the Zeeman-splitting of the 22GHz H₂O masers toward NGC7538-IRS1. The European VLBI Network and the MERLIN telescopes were used to measure the linear polarization and the Zeeman-splitting of the 6.7GHz CH₃OH masers toward the same region. We detected 17 H₂O masers and 49 CH₃OH masers at high angular resolution. We detected linear polarization emission toward two H₂O masers and toward twenty CH₃OH masers. The CH₃OH masers, most of which only show a core structure, seem to trace rotating and potentially infalling gas in the inner part of a torus. Significant Zeeman-splitting was measured in three CH₃OH masers. No significant (3σ) magnetic field strength was measured using the H₂O masers. We also propose a new description of the structure of the NGC7538-IRS1 maser region.