VLBI astrometry of a water maser source in the Sgr B2 complex with VERA

Abstract

We have conducted astrometric observations toward a 22 GHz water maser source associated with the Sgr B2 complex in the Galactic center region with VERA (VLBI exploration of Radio Astrometry). We measured a trigonometric parallax and absolute proper motion of the Sgr B2 complex with respect to an extra-galactic source by observing the water maser source at 10 epochs from 2014 to 2017. The measured distance was 7.52+3.01−1.67 kpc for the Sgr B2M region.We also succeeded to measure internal motions of maser spot…