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Mean-pairwise peculiar velocity in cosmological N-body simulations: time-variation, scale-dependence and stable condition

Toshiyuki Fukushige·Yasushi Suto
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Abstract

We report on the detailed analysis of the mean-pairwise peculiar velocity profile in high-resolution cosmological N-body simulations ($N=8.8\times 10^6$ particles in a sphere of $50 \sim 200$Mpc radius). In particular we examine the validity and limitations of the stable condition which states that the mean {\it physical} separation of particle pairs is constant on small scales. We find a significant time-variation (irregular oscillatory behavior) of the mean-pairwise peculiar velocity in nonlinear regimes. We argue that this behavior is not due to any numerical artifact, but a natural consequence of the continuous merging processes in the hierarchical clustering universe. While such a time-variation is significant in a relatively local patch of the universe, the global average over a huge spatial volume $\simgt$(200Mpc)$^3$ does not reveal any {\it systematic} departure from the stable condition. Thus we conclude that the mean-pairwise peculiar velocity is rather unstable statistics but still satisfies the stable condition when averaged over the cosmological volume.

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Toshiyuki Fukushige, Yasushi Suto. 2001-07-02. Mean-pairwise peculiar velocity in cosmological N-body simulations: time-variation, scale-dependence and stable condition. https://doi.org/10.1086/323042

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