SiO maser survey in the galactic center region with a multi-beam receiver

Abstract

We have made a wide-field survey of SiO masers in the 7′ × 13′ area around the Galactic center with the Nobeyama 45-m radio telescope using a 2 × 3 multi-beam SIS mixer receiver at 43 GHz. We detected 9 SiO maser sources (6 of them are new); newly detected 6 sources have not been identified with Miras or OH 1612 MHz maser sources. The source surface number density, ∼ 360 per square degree, found in this survey is slightly smaller than the number density of OH 1612 MHz sources in the same area. A least-squares analysis of the radial velocities of the detected sources has revealed a rapid rotation of the stars around the Galactic center. This implies that most of the objects detected in this survey belong to the nuclear disk near the Galactic center.