Study of the Galactic Structure using Astrometric Microlensing

天体测量微透镜效应（由恒星、macos和星系的引力透镜效应引起的位置位移）对研究我们星系的结构很有用。(1)银河系MACHO晕分布的天体测量研究我们估计了MACHO引起的银河系外恒星微弧秒级天体测量微透镜的光学深度和事件率。对于LMC和SMC中的恒星，1微弧秒探测阈值的光学深度为0.1数量级，1微弧秒/年的诱导固有运动事件率为0.001/年数量级。它们取决于透镜和光源的分布。这对LMC和SMC中光度自透镜的期望概率有一定的限制。(2)朝向银河系中心的大透镜Sgr A^*的运动是通过参考银河系中心方向的qso来测量的。观测中提到的qso接近天球上的Sgr A^*。这意味着我们观察这些质量黑洞，更多的是通过恒星密集分布的核心、凸起和星系盘。因此，观测到的qso位置可能会因前景物体（例如恒星和银河系本身）的引力偏转而变化。我们考虑了宏观透镜效应，星系核心和凸起的集体引力偏转。它的大小是1微弧秒/年。然而，这种影响是重要的，因为它有一个长期的组成部分。对这些效应的测量将为我们提供有关银河系中心密度和质量函数的宝贵信息。(3)通过引力透镜发现冷行星引力微透镜事件可以揭示围绕前景借出恒星运行的系外行星。我们利用光度微透镜观测的MOA项目发现了这颗5.5地球质量的冷行星。(4) TAGO事件。我们报告了在稀疏的恒星场中一颗非常近（1kpc）的明亮恒星上观测到的第一个引力微透镜事件。塔哥在2006年10月31日发现了仙后座附近的这一事件。光曲线分析表明，这一事件是由引力微透镜引起的，而不是真正的变星。在附近的恒星上证明如此高的放大倍数的可能性要小得多。这可能只是一个好运气，或者由于（未知的）低质量恒星分布函数在我们星系的磁盘结构上，真实的事件发生率比预期的要高。少

Astrometric Microlensing(the positional shift due to gravitational lens effect by stars, MACHOs and the Galaxy) is useful to study the structure of our galaxy.(1)Astrometric study of MACHO halo distribution in our GalaxyWe estimated the optical depth and event rate of micro-arcsecond level astrometric microlensing for the stars outside our galaxy caused by MACHOs. For the stars in the LMC and the SMC, the optical depth of 1 micro-arcsecond detection threshold is on the order of 0.1 and the event rate of the induced proper motion of 1 micro-arcsecond/year is on the order of 0.001/yr. They depend on the distribution of lenses and sources. This poses a constraint on the expected probability of photometric self-lensing in LMC and SMC.(2)Macrolens toward the Galactic CenterThe motion of Sgr A^* has been measured by referring to QSOs in the direction of Galactic Center. The QSOs referred in the observations are close to Sgr A^* on the celestial sphere. This means that we observe these QSOs t … More hrough the core, the bulge, and the disk of the Galaxy where stars are very densely distributed. Therefore, the observed position of QSOs may vary due to the gravitational deflection by foreground objects, e.g. stars and our Galaxy itself. We consider the macro lens effect, the collective gravitational deflection by the core and the bulge of the Galaxy. Its magnitude is the order of 1 micro-arcsecond/yr. However, this effect is important because it has a secular component. The measurement of these effects will provide us valuable information on the density and mass function of the Galactic Center.(3)Discovery of the cool planet through gravitational lensingGravitational Microlensing events can reveal extraSolar planet orbiting the foreground lending stars. We found the cool planet of 5.5 Earth masses by MOA project for investigating the structure in our galaxy using photometric microlensing observation.(4)TAGO Event.We report the observation of the first gravitational microlensing event on a very close(1kpc) bright star in a sparse stellar field. A. Tago discovered this event on 31 October 2006 towards the Cassiopeia constellation. The light curve analyses indicate that this event was caused by the gravitational microlensing rather than a genuine variable star. The provability of such a high magnification in nearby stars is much small. This may be just a good luck, or true event rate is higher than expected due to (unknown) low mass star distribution function on disk structure in our galaxy. Less