Systematic Study for Void Cosmology

Atsushi J. Nishizawa

Cosmic void is a largest structure in the Universe, surrounded by a lot of rich structures such as filaments or clusters. Typical sizes of void range from 10 Mpc/h to 100 Mpc/h. The void is considered to be an intrinsically spherical object in the Universe and can be used in the context of cosmography. Density contrast around the void is of order unity and thus the gravitational non-linearity is thought to be rather weak compared to the one in the cluster region where the density fluctuations are typically of order 100. However, lack of the knowledge about the velocity distribution of the particles which form the void pretends us to precisely predict the shape of the void in the redshift space: i.e. the Redshift Space Distortion (RSD). We conducted a suite of high-resolution N-body simulations and found a potential ability of void to constrain the geometry of the Universe. At the same time, systematic effects arose from the assumptions related to the shape of the void and velocity distribution are also discussed. In particular, we discuss about the feasibility and possible systematics on constraining dark energy parameters, such as density parameter and equation of state parameters.