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Title: STOCHASTIC MODEL OF THE SPIN DISTRIBUTION OF DARK MATTER HALOS

We employ a stochastic approach to probing the origin of the log-normal distributions of halo spin in N-body simulations. After analyzing spin evolution in halo merging trees, it was found that a spin change can be characterized by a stochastic random walk of angular momentum. Also, spin distributions generated by random walks are fairly consistent with those directly obtained from N-body simulations. We derived a stochastic differential equation from a widely used spin definition and measured the probability distributions of the derived angular momentum change from a massive set of halo merging trees. The roles of major merging and accretion are also statistically analyzed in evolving spin distributions. Several factors (local environment, halo mass, merging mass ratio, and redshift) are found to influence the angular momentum change. The spin distributions generated in the mean-field or void regions tend to shift slightly to a higher spin value compared with simulated spin distributions, which seems to be caused by the correlated random walks. We verified the assumption of randomness in the angular momentum change observed in the N-body simulation and detected several degrees of correlation between walks, which may provide a clue for the discrepancies between the simulated and generated spin distributionsmore » in the voids. However, the generated spin distributions in the group and cluster regions successfully match the simulated spin distribution. We also demonstrated that the log-normality of the spin distribution is a natural consequence of the stochastic differential equation of the halo spin, which is well described by the Geometric Brownian Motion model.« less
Authors:
 [1] ;  [2] ; ;  [3]
  1. Center for Advanced Computation, Korea Institute for Advanced Study, Heogiro 85, Seoul 130-722 (Korea, Republic of)
  2. Department of Astronomy and Space Science, Kyung Hee University, Gyeonggi 446-701 (Korea, Republic of)
  3. School of Space Research, Kyung Hee University, Gyeonggi 446-701 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22520145
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 220; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BROWNIAN MOVEMENT; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; CORRELATIONS; DIFFERENTIAL EQUATIONS; GRAPH THEORY; MASS; MEAN-FIELD THEORY; NONLUMINOUS MATTER; RANDOMNESS; RED SHIFT; SPIN; STAR ACCRETION; STOCHASTIC PROCESSES