The Study Of Cosmic Void In The Universe

We study the evolution of cosmic void and the differences between galaxy void and dark matter void with a suite of high-resolution N-body simulations and mock galaxies produced by semi-analytic model.Using the method of void finder without watershed transforming(VIDE)we identify voids in 6 snapshots from z=2.03 to 0.For each void sample we investigate the statistical properties of void evolution from DM voids and galaxy voids,respectively.We compare the relative differences such as abundance,number,shape,effective radius,stacked density profile and find that the number of voids decreased gradually with redshift,the internal density of void becomes deeper,the volume increases,and the shape of voids tend to be more elliptical.The ratios of void statistical properties such as void number,mean effective radius,mean ellipticity of dark matter void to those of galaxy voids show linear relationship with redshift.More-over,the density contrast of small voids tend to be lower than that of the large ones for both population of tracers,which make small voids easily to merge and evolve more vi-olently.Due to that galaxies always follow the high density region of dark matter field,galaxies can not accurately trace the weak wall structures of dark matter voids which make galaxy void merge earlier than dark matter voids.For the galaxy voids,the sur-rounding dark matter density tend to be very high even at the weakest position at the ridge of void,which not only keep the position of galaxy stable but also likely trigger the formation of new galaxies at late time,thus suppress the merging of galaxy voids,and our results show that dark matter voids evolve more violently than galaxy voids.