Science with VERA: VLBI exploration of radio astrometry

VERA (VLBI Exploration of Radio Astrometry), being promoted by National Astronomical Observatory of Japan in collaboration with several Japanese universities, is a new VLBI array for phase referencing astrometry approved to start its construction in 2000. VERA, the first VLBI array dedicated to phase referencing VLBI, has a dual beam antenna system which enables us to observe a Galactic maser source and a nearby reference source simultaneously to remove the atmospheric fluctuation, and will measure positions of Galactic maser sources relative to reference sources (QSOs and radio galaxies) with 10 microarcsec level accuracy. With that accuracy, VERA will be able to determine parallaxes and proper motions of maser sources in the whole Galaxy. The major science targets of VERA will include 3D structure of the Galaxy and the distribution of dark matter, physics of outflow in star forming regions and stellar envelopes, precise calibration of the period-luminosity relation of Mira-type stars, and structure and evolution of QSOs and radio galaxies.