类银河系卫星星系系统的平面演化统计

Statistics on the evolution of the MilkyWay-like satellite galaxy planes

银河系的卫星星系倾向于分布在一个平面上,研究这种平面分布的形成原因有助于人们理解标准宇宙学模型和暗物质晕中的星系分布.使用半解析星系形成模型,通过从统计角度追踪卫星星系平面性的演化历史对类银河系卫星星系呈平面分布的现象进行研究.使用半解析星系模型产生的模拟数据,以与银河系系统质量相当为主要限制条件,按当前卫星星系分布的平面性程度选取3个子样本,分别用恒星质量最大的11颗或前20%的卫星星系的质量张量对应的短长轴比(c/a)表征平面性,计算了近~10 Gyr内3个子样本的整体演化情况.结果表明:在统计上,大部分平面性结构是过渡性的短暂现象.虽然用c/a表征的平面性会受计入卫星数目的影响,但上述结论对用质量最大的前20%卫星星系计算c/a的样本依然成立.

The satellite galaxies of theMilkyWay tend to be distributed on a plane,so the study on this phenomenon may help to understand the standard cosmological model and the distribution of satellites in dark matter halos.The planar distribution of Milk Way-like satellite galaxies was studied by tracing the flatness history statistically based on a semi-analytic galaxy formation model.Three sub-samples were selected according to the flatness of satellite galaxy distribution using simulated data of Guo2011 model when restricted condition is their masses are similar to theMilkyWay system mass.The flatness was measured by the ratio of short and long axis(c/a)from the mass tensor of themostmassive 11 or the top 20%satellites.The whole evolutions of three subsamples in 10 Gyr were calculated.The results show that the most planar structures statistically are transitional transients,and this conclusion still stands when consideringmostmassive of the top 20%satellite galaxies,although the flatness which is represented by c/a is effected by the number of satellites included.