A Determination of Dark Matter Bispectrum with a Large Set of NBody Simulations
Abstract
We use a set of numerical Nbody simulations to study the largescale behavior of the reduced bispectrum of dark matter and compare the results with the secondorder perturbation theory and the halo models for different halo mass functions. We find that the secondorder perturbation theory (PT2) agrees with the simulations fairly well on large scales of k < 0.05 h Mpc^{1}, but it shows a signature of deviation as the scale goes down. Even on the largest scale where the bispectrum can be measured reasonably well in our simulations, the inconsistency between PT2 and the simulations appears for the colinear triangle shapes. For the halo model, we find that it can only serve as a qualitative method to help study the behavior of Q on large scales and also on relatively small scales. The failure of secondorder perturbation theory will also affect the precise determination of the halo models, since they are connected through the 3halo term in the halo model. The 2halo term has too much contribution on the large scales, which is the main reason for the halo model to overpredict the bispectrum on the large scales. Since neither of the models can provide a satisfying description for the bispectrum on scales k ~ 0.1 h Mpc^{1} for the requirement of precision cosmology, we release the reduced bispectrum of dark matter on a large range of scales for future analytical modeling of the bispectrum.
 Publication:

The Astrophysical Journal
 Pub Date:
 June 2009
 DOI:
 10.1088/0004637X/698/1/479
 arXiv:
 arXiv:0904.3200
 Bibcode:
 2009ApJ...698..479G
 Keywords:

 cosmology: theory;
 dark matter;
 galaxies: formation;
 gravitational lensing;
 Astrophysics  Cosmology and Extragalactic Astrophysics
 EPrint:
 10 pages, 7 figures, accepted for publication in ApJ