Data Guide | Bolshoi

This simulation is good for ...

  • Modelling galaxies with stellar mass above ~10^7.5 Msun
  • Probing scales up to 250 h^-1 Mpc (without repetition)
  • Resolving small structures with high time resolution


The Bolshoi simulation was run with the Adaptive Refinement Tree (ART) code. It has nearly the same number of particles as Millennium, but was catered to high resolution rather than a large box size. It is, therefore, favourable for working with satellite galaxies and low-density environments. Full details of the simulation can be found in the paper by Klypin et al. (2011).

Relative size

  • Box length: 250 h^-1 Mpc

The volume relative to Millennium and an all-sky survey out to z=0.05:

Mass resolution

  • Particle mass: 1.35 × 10^8 h^-1 Msun
  • Gravitational softening: 1 h^-1 kpc
  • Number of particles: 2048^3
  • Number of snapshots to z=0: 181

The particle size compared to Millennium:

Bolshoi has 6.37 times higher mass resolution than Millennium, meaning a Bolshoi halo contains 6.37 times the number of particles of a Millennium halo of equivalent mass.


The cosmological parameters for Bolshoi are based on WMAP-7 data (Jarosik et al. 2011), but maintain consistency with earlier WMAP releases.

  • Ω_M = 0.27
  • Ω_Λ = 0.73
  • Ω_b = 0.0469
  • σ_8 = 0.82
  • n = 0.95
  • h = 0.7


Haloes and subhaloes were identified using ROCKSTAR, with merger trees subsequently built with CONSISTENT-TREES. Where other codes might only use the positions of particles to build haloes, ROCKSTAR uses the velocities of particles as well. The trees follow all (sub)haloes down to as few as 2 particles.