The Influence of Redshift Space Distortion on the Cosmic Voids

Abstract

In order to investigate redshift space distortion effect on voids, VIDE (Void Identification and Examination toolkit) algorithm is used 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 the mean radial density profile of “collapsed” voids is significant higher than that of “expanded” voids. Using the member galaxies to match the voids in two spaces, the comparison of the voids’ number distributions of two spaces shows that the difference of voids’ number between them is related to the voids’ size, and half of the voids in redshift space can not matched to the voids in real space. For the matched voids, the redshift space 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.