New Fitting Formula for Cosmic Nonlinear Density Distribution
Résumé
We have measured the probability distribution function (PDF) of a cosmic matter density field from a suite of N-body simulations. We propose the generalized normal distribution of version 2 (${{ \mathcal N }}_{{\rm{v}}2}$) as an alternative fitting formula to the well-known log-normal distribution. We find that ${{ \mathcal N }}_{{\rm{v}}2}$ provides a significantly better fit than that of the log-normal distribution for all smoothing radii (2, 5, 10, 25 [Mpc h (−)(1)]) that we studied. The improvement is substantial in the underdense regions. The development of non-Gaussianities in the cosmic matter density field is captured by continuous evolution of the skewness and shift parameters of the ${{ \mathcal N }}_{{\rm{v}}2}$ distribution. We present the redshift evolution of these parameters for aforementioned smoothing radii and various background cosmology models. All the PDFs measured from large and high-resolution N-body simulations that we use in this study can be obtained from the web site https://astro.kias.re.kr/jhshin.