2.1  :  Simulation

The Millennium Simulation (MR)

This site makes the results of two simulations based on the WMAP1 cosmology available to the public. The first of these, the milli-Millennium simulation, is available in both the public and the protected are of this site and was run as the precursor to the much larger Millennium simulation. The simulations were performed by Volker Springel of the MPA using a specially customized version of the GADGET 2 simulation code. Both are pure dark matter simulations in a periodic cubic box. The difference between the two is the size of the box, which is 62.5 Mpc/h for the milli-Millennium, and 500 Mpc/h for the Millennium simulation, and the number of particles, which was 270³ and 512 times that much for the milli-Millennium and Millennium respectively. The other parameters such as cosmology and resolution were the same.

The simulation parameters for the Millennium simulation are as follows:

• Ω_m = Ω_dm+Ω_b = 0.25
  density parameter (ρ_m/ρ_crit) in total matter
• Ω_b = 0.045
  density parameter in baryons
• Ω_Λ = 0.75
  density parameter of dark energy
• h = H₀/100 km/s/Mpc = 0.73
  Hubble parameter in units 100 km/s/Mpc
• n = 1
  slope initial power spectrum
• σ₈ = 0.9
  mass density fluctuation amplitude in 8 Mpc/h sphere at present
• m_p = 8.61 x 10⁸ M_sun/h
  particle mass in solar masses
• L = 500 Mpc/h
  size of the cubic simulation box
• Number of particles = 2160³

For further details see V. Springel et al. 2005, Nature 435, 629

The Millennium WMAP7 Simulation (MR7)

The protected area of the site also makes available models based on a version of the Millennium Simulation using the WMAP7 cosmology. This run is referred to as MR7 in database and table names. The simulation parameters for this run are as follows:

• Ω_m = Ω_dm+Ω_b = 0.272
  density parameter (ρ_m/ρ_crit) in total matter
• Ω_b = 0.0455
  density parameter in baryons
• Ω_Λ = 0.728
  density parameter of dark energy
• h = H₀/100 km/s/Mpc = 0.704
  Hubble parameter in units 100 km/s/Mpc
• n = 0.967
  slope initial power spectrum
• σ₈ = 0.81
  mass density fluctuation amplitude in 8 Mpc/h sphere at present
• m_p = 9.31 x 10⁸ M_sun/h
  particle mass in solar masses
• L = 500 Mpc/h
  size of the cubic simulation box
• Number of particles = 2160³

Details of this simulation are described in Guo etal (2013) where it is refered to by the name MS-W7. The linear phases used for the MR7 initial conditions are taken from Panphasia - the public multi-scale Gaussian white noise field described in Jenkins 2013. The phases for the MR7 simulation are published in table 6 of Jenkins 2013, where the name MW7 is used.