红移畸变对宇宙学空洞的影响

为探索红移畸变对空洞性质的影响, 利用了一组星系形成半解析模拟星表数据, 采用VIDE (Void Identification and Examination toolkit)算法寻找真实空间和红移空间的宇宙学空洞, 根据空洞外围墙结构处的星系运动速度将空洞分为``塌缩型''和``膨胀型''. 结果表明: ``塌缩型''空洞所占比例会随着空洞的尺度变大而减少, ``膨胀型''空洞则与之相反, 两类空洞的平均有效半径在实空间中相差20%, ``塌缩型''空洞的平均径向密度轮廓显著高于``膨胀型''空洞. 利用成员星系将两种空间中的空洞进行匹配, 通过比较实空间和红移空间中空洞的数目分布, 发现实空间和红移空间中空洞的数目差异与空洞大小有关, 并且红移空间中有一半左右的空洞无法对应到实空间. 对匹配空洞, 红移畸变对``塌缩型''空洞的密度影响更大; 对未匹配空洞, 其密度轮廓与匹配空洞存在明显区别, 并且实空间中未匹配空洞其壳层星系向空洞内部运动的趋势更加明显.

The Influence of Redshift Distortion on the Cosmic Voids

In order to investigate redshift distortion effect on voids, VIDE (Void Identification and Examination toolkit) algorithm is uesed to find cosmic voids in real space and redshift space based on a mock galaxy catalog produced by the semi-analytical galaxy formation model. The voids can be divided into ``collapsed'' type and ``expanded'' type, according to the galaxy velocity on the void wall. The results show that the fraction of the ``collapsed'' voids decrease as the voids size grows, while ``expanded'' voids are contrary. The effective radius of two type voids differs by 20% in real space and mean radial density profile of ``collapsed'' void is significant higher than ``expanded'' voids. Using the member galaxies to match the voids in two spaces, the comparison of the voids number distributions of two space shows that the difference of voids number between them is related to the void size, and half of the voids in redshift space can not matched to the voids in real space. For the matched voids, the redshift distortion has stronger effect on the density profile of the ``collapsed'' voids; for the unmatched ones, their density profile is clearly different, and the infall movement of galaxies on their shell is more obvious in real space.