Hierarchical pancaking: Why the Zel'dovich approximation describes coherent large scale structure in N body simulations of gravitational clustering
Sep 26, 199419 pages
Published in:
- Mon.Not.Roy.Astron.Soc. 274 (1995) 99-109
e-Print:
- astro-ph/9408019 [astro-ph]
Report number:
- NONE
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Abstract: (arXiv)
To explain the rich structure of voids, clusters, sheets, and filaments apparent in the Universe, we present evidence for the convergence of the two classic approaches to gravitational clustering, the ``pancake'' and ``hierarchical'' pictures. We compare these two models by looking at agreement between individual structures -- the ``pancakes'' which are characteristic of the Zel'dovich Approximation (ZA) and also appear in hierarchical N-body simulations. We find that we can predict the orientation and position of N-body simulation objects rather well, with decreasing accuracy for increasing large- (small scale) power in the initial conditions. We examined an N-body simulation with initial power spectrum , and found that a modified version of ZA based on the smoothed initial potential worked well in this extreme hierarchical case, implying that even here very low-amplitude long waves dominate over local clumps (although we can see the beginning of the breakdown expected for ). In this case the correlation length of the initial potential is extremely small initially, but grows considerably as the simulation evolves. We show that the nonlinear gravitational potential strongly resembles the smoothed initial potential. This explains why ZA with smoothed initial conditions reproduces large-scale structure so well, and probably why our Universe has a coherent large-scale structure.Note:
- 17 pages of uuencoded postscript. There are 8 figures which are too large to post here. To receive the uuencoded figures by email (or hard copies by regular mail), please send email to: jenny@kusmos.phsx.ukans.edu. This is a revision of a paper posted earlier now in press at MNRAS
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