银河系中球状星团的空间分布和运动轨道  

Space Distribution and Motional Orbits of Globular Clusters in the Galaxy

作　　者：王龙[1] 周洪楠[1] 

机构地区：[1]南京师范大学物理科学与技术学院,南京210097

出　　处：《天文学报》2002年第3期302-326,共25页Acta Astronomica Sinica

摘　　要：选用银河系中29个累积光谱型为F型的球状星团样本.根据它们的视向速度,绝对自行等参数,归算处理后得出了各样本星团的空间分布和运动速度.并以此作为初始条件,在给定的3种银河系引力势模型中,采用数值积分方法计算出各样本星团的运动轨道.计算结果表明:(1)大部分样本星团都位于银心距5kpc-10kpc的范围内,相对于银心呈球对称分布,它们的速度也呈椭球分布;(2)29个样本星团按其金属度大小和基本性质分类,可分属HB和MP两个次系,且样本星团数随金属度[Fe/h]而变化,在[Fe/h]=-1.6处出现一个峰值;(3)所有样本星团的轨道运动都呈周期性,大都在一个有界而不封闭的周期轨道上运动,其最大银心距大都在40kpc以内.不同的引力势模型对球状星团轨道的具体形态影响不大,在给定的引力势模型下,当某些星团的运动轨道穿越距银心1kpc附近的区域时会出现“混沌’行为.而样本星团的金属度与其轨道形态之间的相关性并不明显;(4)29个样本星团的轨道半长轴、远银心距和方位周期随金属度的变化规律基本相似.轨道偏心率与金属度有关,对于所选的晕族样本星团而言,大约有24％的样本星团的轨道偏心率低于0.4.不同的引力势模型对近银心距、偏心率和参数的不确定度等量影响较小,但是对远银心距、径向周期和方位周期等参数影响较为明显.The 29 F globular clusters in the galaxy are selected as samples. According to the basic data, radial velocities and proper motions of sample clusters, the initial positions and velocities of the samples are reduced using the galactic coordinates, and their orbits are integrated by numerical method for three different Galactic gravitational potential models. The calculating results show: (1) most of samples are located in 5kpe-10kpe from Galactic center. All of the sample clusters present a spherical symmetrical distribution around the Galactic center, and their space velocities are presented a ellipsoidal distribution; (2) According to the metallicity and basic characters, the sample clusters are separated into HB subgroup and MP subgroup. The number of samples are changed with metallicity [Fe/H], and there is a peak at [Fe/H]=-1.6; (3) The orbits of sample clusters show mostly limited, periodic characteristics, but the orbits are not closed completely, their maximal galactocen-tric distance -is less than 40kpe. The differences in orbital morphologies due to different potentials is slighting, however, given a certain potential, for clusters that have perigalactic distance smaller than 1kpe, some orbits may exhibit a chaotic behavior. The correlation between the metallicity of samples and the orbital morphologies is unclearly; (4) It is found that the semi-major axis, apogalactic distance and azimuth period of 29 sample clusters are changed with their metallicity similarly, but a obvious correlation is seen between orbital eccentricity and metallicity. There is a fraction of 24% of the sample clusters with eccentricities lower than 0.4. The different Galactic gravitational potential have not clear influence upon the perigalactic distance, eccentricity and uncertainty of orbital parameters, but which is significant for other parameters, such as the apogalactic distance, semi-major axis, radial period and azimuth period and so on.

关 键 词：银河系 球状星团 空间分布 运动轨道 

分 类 号：P154.12[天文地球—天文学]