## MDR1

MDR1 is the first MultiDark simulation, performed in 2010. A detailed description is available in the paper Prada et al. 2011, arXiv:1104.5130. This simulation contains about 8.6 billion particles in a (1 Gpc/h)^{3} cube and thus has a larger volume than the Millennium Simulation, using the more up-to-date WMAP5 cosmology.

Also see Simulations overview for an overview of all available and planned cosmological simulations.

Please give proper Credits when using data from this simulation.

### Details

Box size | 1 Gpc/h | side length of the cosmological cube |

Number of particles | 2048^{3} |
total number of dark matter particles |

Mass resolution | 8.721*10^{9} M_{sun}/h |
mass of one dark matter particle |

Force resolution | 7 kpc/h | physical force resolution |

Initial redshift | 65 | redshift at which the simulation started |

Cosmology | ||

h | 0.70 | Hubble parameter |

Ω_{Λ} |
0.73 | density parameter for dark energy |

Ω_{m} |
0.27 | density parameter for matter (dark matter+baryons) |

Ω_{b} |
0.0469 | density parameter for baryonic matter |

n | 0.95 | normalization of the Power spectrum |

σ_{8} |
0.82 | amplitude of mass density fluctuation in 8 Mpc/h sphere (at redshift z=0) |

Other constants | ||

G | 6.67428 * 10^{-8} cm^{3} g^{-1} s^{-2} |
Gravitational constant (Rev. Mod. Phys. 80 (2008) 633-730) |

1 Mpc | 30.85677 * 10^{23} cm |
1 Mpc in cm |

M_{sun} |
1.98892 ± 0.00025 10^{33} g |
Solar mass (Physics Reports 281 (1997) 309) |

### MDR1 data in the database

The following table provides an overview on the database tables which are available for this simulation. For each table, a link to its “table type” is given, which leads to a page explaining the individual columns of the corresponding table in more detail.

Several tables (halo catalogues, particle tables) contain a Peano-Hilbert key for each row, which can be constructed from the position using the hilbert key function. If not indicated otherwise, the hilbert order for this simulation is 10, i.e. there are 2^{10} = 1024 cells per dimension.

Database table | Table type | Short description |
---|---|---|

AvailHalos | AvailHalos | Gives an overview on the snapshots, for which halo data are stored in the FOF or BDM tables. |

AvailParticles | AvailParticles | Gives an overview for which snapshots there are raw particle data available. |

BDMV | BDM | BDM (Bound Density Maximum) catalogue for all available snapshots, calculated using the standard overdensity criterion with 360*ρ (background density)._{back}`bdmId = ( snapnum*10` |

BDMVProf | BDMProf | Halo profiles of the BDMV catalogue for all available snapshots, calculated using the standard overdensity criterion with 360*ρ (background density)._{back} |

BDMW | BDM | BDM catalogue for all available snapshots, calculated using 200*ρ (critical density) for defining the halo boundary._{crit}`bdmId = ( snapnum*10` |

BDMWProf | BDMProf | Halo profiles of the BDMW catalogue for all available snapshots, calculated using the standard overdensity criterion with 360*ρ (background density)._{back} |

BDMWMfreq | Mfreq | Galaxy cluster catalogue for distinct halos from the BDMW catalogue with a total mass (Mtot) above 10^{14} M_{sun}/h, only for snapshots corresponding to the redshift values z = 0, 0.05, 0.1, 0.16, 0.18, 0.2, 0.27, 0.32, 0.37, 0.4, 0.47, 0.53, 0.61, 0.69, 0.78, 0.89 and 1. |

Dens512_z0 | Dens | Density field for redshift 0, for 512^{3} grid cells |

Dens1024_z0 | Dens | Density field for redshift 0, for 1024^{3} grid cells |

FOF | FOF | Main Friends-of-Friends catalogue for all available snapshots, level 0 (relative linking length 0.17);`fofId = (snapnum*10 + level)*10` |

FOF1-FOF4 | FOF | Friends-of-Friends catalogue for all available snapshots, same as FOF-table, but for smaller (relative) linking lengths, levels 1 (linking length 0.085) to 4 (linking length 0.010625). Thus these tables contain substructures of the FOF groups. |

FOFc | FOF | Friends-of-Friends catalogue for all available snapshots, computed with the commonly used linking length 0.2, as was used first by White et al. 1987. The corresponding average overdensity with this value is about 400 – contrary to the popular belief of 200 (see More et al. 2011. The level-column is replaced here by a linkLength_rel column, which provides the used linking length directly. |

FOFMtree | FOFMtree | Merger trees for top level FOF groups (level=0) with > 2 * 10^{12} M_{sun}/h from redshift 0. Substructures are not taken into account. |

FOFParticles | FOFParticles | Table for connecting FOF groups from the FOF table with its particles, at the moment for redshift 0 (`snapnum=85` ) only. |

FOFParticles1 – FOFParticles4 | FOFParticles | Corresponding tables for connecting FOF groups from tables FOF1 – FOF4 to their particles for redshift 0. |

FOFParticles## | FOFParticles | Corresponding tables for connecting FOF groups from the main FOF table with their particles## for redshift ##. |

FOFScl | FOFsub | FOF superclusters; contains Friends-of-Friends catalogues for redshift 0, for 7 different (relative) linking lengths between 0.35 (sclevel 0) and 0.17 (sclevel 6)), i.e. much larger objects (superclusters) than in the FOF table. It also contains identifiers for building substructure trees |

FOFSclParticles_85_l0 – …l6 | FOFParticles | Table for connecting FOF groups from the FOFScl superclusters table with its particles; the number at the end indicates the level of substructure |

FOFSub | FOFsub | FOF substructure tree connecting the FOF – FOF4 catalogues at `snapnum=85` (z=0). |

LinkLength | LinkLength | Overview on levels for FOF groups and corresponding linking lengths (for FOF, FOF1 – FOF4 tables) |

LinkLengthScl | LinkLength | Overview on sclevels for superclusters and corresponding linking lengths (for FOFScl table) |

Particles, Particles## | Particles | All simulation particles for various snapshots (denoted by ##) with their positions and velocities.A list of all available snapshots can be obtained from table `AvailParticles` . |

Redshifts | Redshifts | Overview on snapshot numbers (snapnum) and corresponding redshifts |

Rockstar | Rockstar | Consistent halo catalogue with merger trees |

TreeSnapnums | TreeSnapnums | Maps between snapshot numbers used in the FOF merger trees for MDR1 and the “usual” snapshot numbers. |

Tweb512 | Web | Eigenvectors and eigenvalues of the gravitational tidal tensor, for a 512^{3} grid |

Tweb1024 | Web | Eigenvectors and eigenvalues of the gravitational tidal tensor, for a 1024^{3} grid |

Vweb512 | Web | Eigenvectors and eigenvalues of the velocity shear tensor, for a 512^{3} grid |

Vweb1024 | Web | Eigenvectors and eigenvalues of the velocity shear tensor, for a 1024^{3} grid |