STUDY OF 3D IMAGE OF PERSEUS-ARM-REGION IN THE GALAXY USING DIFFERENTIAL VLBI

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(1)The observations of a pair of water vapor maser sources, W49N and OH 43.8-0. 1, were carried out using the dual-beam VLBI system named VERA (VLBI Exploration of Radio Astrometry). While the residual fringe phases of both sources showed rapid variations over 360deg due to the atmospheric fluctuation, the differential phase between the two sources is very small, demonstrating that the atmospheric phase fluctuation was effectively removed by dual beam phase referencing.(2)A magnetic field mapping of water vapor maser clouds in the star-forming region W3 IRS5, which is in the Perseus Arm, has been made on the basis of the linear Polarization VLBI observation. Using the VLBA at 22.2GHz, 16 of 61 detected water masers were found to be linearly polarized with polarization degree up to 13%. The magnetic field vectors are roughly perpendicular to the spatial alignments of the maser features.(3)Mizusawa 10m antenna has performed monitoring observations of light curve and polarization of the maser spots around Ori-KL region. The antenna has 22GHz and 43GHz receivers, which are able to detect water vapor masers and SiO masers around late-type stars. The system has good performance for linear polarization measurement.(4)Proper-motion measurements of water vapor masers in the massive-star forming region W51A were carried out using Japanese VLBI network (J-Net). Analyses of the 3-D kinematics of the masers in three maser clusters of W51A indicates that the distance of it is 6.1±1. 3kpc based on a model-fitting method adopting a radially expanding flow.(5)SiO maser sources are surveyed towered large-amplitude variables within 15' of the Galactic center, resulting in 79 detections and 58 non-detections.(6)Monitoring differential VLBI has been performed toward one of the famous massive star forming region W3OH in the Perseus arm using VERA with water vapor maser line in order to study the 3-D position of it in the Perseus arm region.