Structure of the Galactic Bulge

在过去的十年里，银河系凸起一直是许多研究的焦点。1991年，我们根据银河系中心周围IRAS源的分布，提出了凸起的非轴对称模型。随后，我们通过对凸起IRAS源的SiO观测发现了凸起的全球旋转。由于先前研究的脉泽源总数只有16个，因此计划在野山射电天文台对凸起脉泽源进行系统调查。用了三年的时间才获得了凸起区域124个震源的径向速度。我们确定凸起旋转速率为9.3km/sec/deg。这与其他方法得到的结果一致。虽然源的数量远远不够完整，但我们仍然注意到凸起的速度结构中一些有趣的特征。首先，平均自转速率随着离银道面距离的增加而减小。用非轴对称凸起形状折衷微分旋转的唯一可行方法似乎是允许凸起内部速度场的存在。其次，有些地区在速度-经度图上几乎没有检测到震源。这些“洞”可能是全面了解速度结构的线索。在南非的萨瑟兰天文台对这些凸起源进行了多次近红外观测。需要更多的数据来确定它们的光变化的精确周期。

The Galactic bulge has been the focus of many researches in the past decade. In 1991 we proposed the non-axisymmetric model of the bulge on the basis of the distribution of IRAS sources around the Galactic center. Subsequently, the global rotation of the bulge was detected by our SiO observation of the bulge IRAS sources.Since the total number of the maser sources in the previous study was only sixteen, systematic survey of the bulge maser source was planned at the Nobeyama Radio Observatory. It took three years to obtain the radial velocities of 124 sources in the bulge area. We determined the bulge rotation rate as 9.3km/sec/deg. which was consistent with those obtained by other methods.Although the number of sources was far from completeness, we still notice some interesting features in the velocity structure of the bulge. First, the mean rotation rate decreses with the distance from the Galactic plane. The only plausible way to compromize the differential rotation with the non-axisymmetric shape of the bulge seems to allow the existence of the internal velocity field inside the bulge. Second, there are areas where few sources were detected on the velocity-longitude diagram. Those 'holes' could be the clues to the full understanding of the velocity structure.Near infrared observation of those bulge sources were repeatedly performed at the Sutherland Observatory in South Africa. More data is needed to determine the precise periods of their light variation.