2.1  :  Simulations

This site makes the results of a suite of simulations available to the public. The first of these is the Millennium Simulation, performed by Volker Springel (MPA) using a specially customized version of the GADGET-2 simulation code. See Springel etal (2005). The second is the Millennium-II Simulation, perfomed by Mike Boylan-Kolchin (MPA) using Volker Springel's GADGET-3 code. See Boylan-Kolchin etal (2009). Both are pure dark matter simulations in a periodic cube using 10,077,696,000 simulation particles. The main differences between the two are the size of the box (500 Mpc/h for Millennium, 100 Mpc/h for Millennium-II), the force resolution (Plummer-equivalent softening of 5 kpc/h for Millennium, 1 kpc/h for Millennium-II), and the particle mass (8.6 x 108 Msun/h for Millennium, 6.9 x 106 Msun/h for Millennium-II).

A smaller version of the Millennium Run, the milli-Millennium Simulation, is also available on this site. This simulation used the same cosmology and resolution as the Millennium Simulation but in a 62.5 Mpc/h box with 19,683,000 particles. A smaller version of the Millennium-II, the mini-Millennium-II was run as well. It had the box size of the Millennium-II, the mass resolution of the Millennium and used the same initial condiftions Forier modes as Millennium-II.

Peter Thomas has run a WMAP7 version of the Millennium run, which will be referred to as MR7 in much of this web site. Details of this simulation are described in Guo etal (2013) where is 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.

The parameters for the various simulations are listed in the first table below. Note that we add a "Code" name for each simulation that is used for table names in various places. For example halo merger trees derived form the simulations and stored in the database MPAHalotrees uses these shorthand names. Similarly for galaxy catalogues derived from these in Guo2013a.

Code Name Ωm = Ωdmb Ωb ΩΛ h = H0/100 km/s/Mpc ns σ8 Np mp (Msun/h) L (Mpc/h) ε (kpc/h)
Plummer-equivalent force softening
MR Millennium 0.25 0.045 0.75 0.73 1 0.9 21603 8.61 x 108 500 5
mMR milli-Millennium (millimil) 0.25 0.045 0.75 0.73 1 0.9 2703 8.61 x 108 62.5 5
MRII Millennium-II 0.25 0.045 0.75 0.73 1 0.9 21603 6.88 x 106 100 1
mMRII mini-Millennium-II (miniMilII) 0.25 0.045 0.75 0.73 1 0.9 4323 8.61 x 108 100 5
MR7 Millennium-WMAP7 0.272 0.0455 0.728 0.704 0.967 0.81 21603 9.31 x 108 500 5

The second table contains entries that do not represent real simulations, but are scaled versions of a real simulation indicated by its code in the "Original simulation" column. Using the scaling algorithm from Angulo & White (2010) one can approximate catalogues as they would have been obtained had the simulation been run with a different cosmology.

Code Original Simulation Ωm Ωb ΩΛ h ns σ8 mp (Msun/h) L (Mpc/h)
MRscWMAP7 MR 0.272 0.0455 0.728 0.704 0.967 0.81 1.063 x 109 521.555
MRIIscWMAP7 MRII 0.272 0.0455 0.728 0.704 0.967 0.81 8.5024 x 106 104.3110