基于LAMOST对银河系晕星轨道偏心率的研究

基于LAMOST的A/F/G/K型巨星样本,通过空间分布和金属丰度分布挑选晕星样本并进一步研究银河系晕星的轨道偏心率。研究发现：在距离银盘5~15 kpc的范围内,晕星的偏心率峰值均在0.8左右,并不随距离的增大而改变,但垂直距离越大时峰值处晕星所占比也越大。在5 <|z|<25 kpc的范围内,内晕星和外晕星在偏心率的分布上有明显的差异：内晕星偏心率的峰值在0.65左右,分布较为弥散;而外晕星偏心率的峰值在0.8左右,大部分集中在e>0.6的区域。这些不同的运动学特征反映了内外晕的形成机制不同。

Study of the stellar orbital eccentricity based on LAMOST survey

Based on A/F/G/K giant stars from LAMOST data,we pick out halo sample stars according to the space and metallicity distribution to study the orbital eccentricity distribution of the halo stars in the Galaxy. We find that the observed halo stellar orbital eccentricity distribution has the peak of 0.8 and it does not change with the distance in the 5<|z|<15 kpc range. In addition, the inner-halo stars and outer-halo stars have different eccentricity distributions in the 5<|z|<25 kpc range. The peak eccentricity of inner-halo is about 0.65, and that of outer-halo is about 0.8. Compared to the inner-halo stars, the outer-halo stars are more concentrated in the area beyond e~0.6. Maybe this different kinematics represents different formation mechanisms of inner-halo and outer-halo.