Observational Study of the SiO Maser Sources at the Galactic Center Region

本研究利用射电望远镜测量了来自晚型恒星的SiO脉泽线中恒星的径向速度，探讨了银河系中心附近环境中的物理现象。我们在h0和H11学年完成了以下无线电和红外观测。(1)利用Nobeyama的45 m射电望远镜在SiO脉泽线上观测到银河系盘中600个颜色选择的IRAS源。，产生300个检测。通过分析获得的恒星径向速度，我们发现一组恒星偏离了从气体运动可知的星系旋转。(2)利用澳大利亚国立大学2.3 m红外望远镜对同一区域约500个光源进行了JHK光度和成像观测。根据视星等，我们估计了到这些天体的距离。从这项研究中，揭示了以下事实。(1)大部分位于离银河系中心10度以内的IRAS源被认为是凸起星。位于银河系中心前面的一组恒星显示出很大的负平均径向速度（-46公里/秒），而位于星系中心后面的恒星则显示出正径向速度。这里的距离是从12微米和25微米的红外强度推断出来的。(3)这一现象被解释为棒状凸起中恒星的流动运动；棒子的近端位于银河系经度的第一象限，恒星轨道沿着棒子势被拉长。德口博士计划并指导了这项研究，并分析了近红外光度数据。三吉博士分析了无线电频谱数据，并进行了VLBI观测。

This research explores the physics in the environment near the galactic center with measuring the radial velocities of stars in the silicon monoxide (SiO) maser lines from late type stars by a radio telescope. We have completed the following radio and infrared observations in Hl0 and H11 academic years. (1) 600 color-selected IRAS sources in the galactic disk have been observed in SiO maser lines with the 45-m radio telescope at Nobeyama., resulting 300 detection. From analyzing the obtained radial velocities of stars, we found a group of the stars being deviant from the galactic rotation which was known from the gas motion. (2) We made the JHK photometric and imaging observations for about 500 sources in the same region with the Australian National Univ. 2.3-m infrared telescope. From the apparent magnitudes, we estimated the distances to the objects.From this research, the following facts are revealed. (1) large percentages of IRAS sources which are located within 10 degree from the galactic center are considered to be the bulge stars. A subset of stars located in front of the galactic center exhibits a large negative (-46 km/s) average radial velocity, and those behind, a positive radial velocity,. Here the distance were deduced from the infrared intensities at 12 and 25 micron. (3) This phenomenon is interpreted as a streaming motion of stars in the bar-like bulge; the near end of the bar is located at the first quadrant of the galactic longitude and the stellar orbits are elongated along the bar potential. Dr. S. Deguchi planned and directed the research and analyzed the near-infrared photometric data. Dr. Miyoshi analyzed the radio spectral data and performed the VLBI observations.