Effects of dark matter pressure on the ellipticity of cosmic voids

Abstract

The dark matter in or around the cosmic voids affects their shapes. The thermodynamical properties of dark matter can alter the ellipticity of cosmic voids. Here, applying the dark matter equation of state from the pseudo-isothermal density profile of galaxies, we explore the shapes of cosmic voids with the non zero pressure dark matter in different cosmological models. For this purpose, the linear growth of density perturbation in the presence of dark matter pressure is calculated. In addition, the matter transfer function considering the dark matter pressure, as well as the linear matter power spectrum in the presence of the dark matter pressure are presented. Employing these results, the probability density distribution for the ellipticity of cosmic voids with the non zero pressure dark matter is calculated. Our calculations verify that the dark matter pressure leads to more spherical shapes for the cosmic voids.