Single-dish and interferometer measurements of water-maser polarization

Abstract

Linear polarization of water-maser emission at 22.235 GHz was measured for astronomical sources using a single-dish telescope and an interferometer (the VLA). Of the 25 star-forming regions observed using single-dish polarimetry, eight had linearly polarized features. None of the 17 stellar maser sources showed measurable (greater than a few percent) linear or circular polarization in the single-dish observations. No linear polarization stronger than 7 percent was detected from the galactic nucleus of NGC 3079. In current theories, the direction of linear polarization is predicted to be parallel or perpendicular to the projection of the magnetic field in protostellar clouds, and thus can potentially provide information on field configurations in these regions if high angular resolution can be achieved. The direction of polarization for a few water-maser spots toward Orion KL, Orion B, NGC 2071, and W51 was successfully mapped using the VLA in continuum mode. These observations are discussed within the context of the theory of molecualr alignment and maser beaming in magnetic fields. 26 refs.