paper

On the Distribution of Haloes, Galaxies and Mass

arXiv:astro-ph/0105008 · doi:10.1046/j.1365-8711.2002.05378.x

Abstract

The stochasticity in the distribution of dark haloes in the cosmic density field is reflected in the distribution function which gives the probability of finding haloes in a volume with mass density contrast . We study the properties of this function using high-resolution -body simulations, and find that is significantly non-Poisson. The ratio between the variance and the mean goes from (Poisson) at to (sub-Poisson) at to (super-Poisson) at . The mean bias relation is found to be well described by halo bias models based on the Press-Schechter formalism. The sub-Poisson variance can be explained as a result of halo-exclusion while the super-Poisson variance at high may be explained as a result of halo clustering. A simple phenomenological model is proposed to describe the behavior of the variance as a function of . Galaxy distribution in the cosmic density field predicted by semi-analytic models of galaxy formation shows similar stochastic behavior. We discuss the implications of the stochasticity in halo bias to the modelling of higher-order moments of dark haloes and of galaxies.

10 pages, 6 figures, Latex using MN2e style. Minor changes. Accepted for publication in MNRAS

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