Cluster Resimulation Project  

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We pick up clusters of various mass from the large-volume high resolution simulations, and resimulate them at a higher mass resolution.

The first stage: N-body Simulation with 5123 particles

A high density model (tauCDM) and a low density model (lambda CDM) are simulated in 320 Mpc/h and 480 Mpc/h boxes, respectively. The calculations have been carried out on the T3E, a parallel supercomputer at RechenZentrum Garching, using a message-passing parallel version of HYDRA. Simulation parameters are tabulated downbelow.

The second stage: Resimulation of clusters with higher mass resolution

Resimulations are done by using GADGET, a serial/parallel Tree-code for N-body/SPH simulations.

The recipe of the resimulation is as follows:

  1. We use a group finding algorithm to locate MANY clusters in the simulation box.
  2. Pick a cluster, mark the particles in it and trace them back to the initial time.
  3. Now we know where the particles were initially. We replace them by a much large number of lower-mass particles, add appropriate fluctuation on small scale, and resimulate the formation of the cluster.

Here is the linkresult from the first sequence of simulations done by Volker Springel.


  • Barbara Lanzoni (IAP, Paris)
  • Volker Springel (MPA, Garching)
  • Bepi Tormen (University of Padova, Padova)
  • Simon White (MPA, Garching)

Simulation parameterstop


Two cosmological models were simulated in larger boxes (479 Mpc/h for LCDM and 321 Mpc/h for tCDM) than those of the Virgo simulations, while keeping higher mass resolution. We find many clusters in the box, which are still well resolved and thus suitable for re-simulation.

Shown in the left panels are projected mass distibutions in a sliced region in the simulation box. Low-density regions which look like "voids" are dark, while blue (and light-green) parts are high-density regions. The pictures were created using an adaptive smoothing scheme which assigns to each particle an individual smoothing length. Thus, high density regions are not smoothed at all whereas low density regions are smoothed.

Lambda CDM


Boxsize 479 Mpc/h
5123 particles
OMEGA = 0.3
LAMBDA = 0.7
H0 = 70 km/(Mpc sec)
Sigma8 = 0.9
Mass per particle 6.86 1010M_sun/h




tau CDM

Boxsize 320.6 Mpc/h
5123 particles
OMEGA = 1.0
LAMBDA = 0.0
H0 = 50 km/(Mpc sec)
Sigma8 = 0.51
Mass per particle 6.86 1010M_sun/h






Data Downloadtop

The data are not yet publically available.


Yoshida et al (Virgo Consortium), 2000, in preparation.


Here is an example of proper credit for these Virgo data.
"The simulations in this paper were carried out by the Virgo Supercomputing Consortium using computers based at Computing Centre of the Max-Planck Society in Garching and at the Edinburgh Parallel Computing Centre. The data are publicly available at"

Comments to: Virgo Administrator virgo@mpa-garching.mpg.detop