银河系自转曲线的测定和研究

The rotation curve of the Milky Way was measured from HI, CO etc., which have very large uncertainties in distance estimation. This leads to an unreliable rotation curve. In this work, for the first time, we will apply red clumps in several lines of sight in the disk to measure a more accurate rotation curve. The red clumps, which cover from 3kpc to 13kpc in Galactocentric radius, will be selected from 2MASS catalog. They are accurate distance indicators, because they have fixed luminosity. However, they are mostly old disk stars, hence we need both the azimuthal velocities and the asymmetric drifts to obtain the rotation curve. Therefore, we have to measure both the line-of-sight velocities and proper motions of the red clumps. The later has been provided by PPMXL catalog. For the former we have obtained about 1000 high quality spectra of red clumps through TAP program last year. And we will apply for more observations through TAP and VLT time. The target is to finally collect 6000-9000 spectra of red clumps in 4-6 lines of sight in the disk..The direct measured rotation curve will be then used to fit the gravitational potential model of the Galaxy and as a result, we will give the distributions of the dark and baryonic matter of the Milky Way. In addition, we may also obtain the information of the possible substructure in the Galactic disk.

以往的银河系自转曲线主要是通过对HI、CO等射电源的测量得到的。由于射电源的距离估计不确定性非常高，因此得到的自转曲线还不是非常可靠。本项目首次通过观测银盘若干视线方向上数千颗红团簇星的视向速度,结合它们的自行更精确地测定银河系的自转曲线。2MASS星表中可以选出大量银盘上的红团簇星，它们是十分精确的标准烛光，覆盖距银心3kpc到13kpc的范围。红团簇星是比较年老的盘星，所以不仅需要测量周向速度，还需要导出非对称流以确定自转曲线。这就需要测量它们的视向速度和自行。自行已经由最近发布的PPMXL星表提供，而我们已经通过TAP项目获得了大约1000条红团簇光谱，并将继续通过申请TAP时间和VLT时间获得更多的视向速度。.观测得到的自转曲线可以进一步和理论研究相结合，拟合银河系引力势模型,探究银河系的暗物质分布、银盘的质量分布以及可能存在的质量子结构。

本项目通过测量银盘中大量存在的红团簇巨星的视向速度，估算银河系的自转曲线，并借助它研究银河系的物质（包括暗物质）分布。我们已经成功地从TAP项目获得三次共计4个晚上的观测时间。其中2.5个晚上已经观测，使用MMT获得约5000红团簇巨星的光谱，完成了银心距9-13 kpc范围内的自转曲线的精确测定。该测量的精度达到13 km/s，是目前世界上测量精度最高的结果。该项研究无论在观测、方法还是精度上均达到国际领先水平。此外，还首次在银河系外盘的反银心方向发现了中心棒激发的恒星轨道共振证据，有效限定了棒的动力学参数。在一年的资助期内在SCI索引的国际国内有影响力的专业期刊发表论文8篇，当年引用总数达到62次。