Constrained Simulations of the Local Galaxy Population

Constrained Simulations of the Local Universe were made in the frame of the GIF consortium, and involved :

H. Mathis (1), G. Lemson (2), V. Springel (1), G. Kauffmann (1), S. D. M. White (1), A. Eldar (2) and A.Dekel (2)

(1) MPA Garching, (2) Hebrew University

introduction/ collisionless runs/ simulation parameters/ references/ HIGH RESOLUTION PICTURES for astro-ph/0111099 and astro-ph/0201193/ DATA-DOWNLOAD/ slices through the simulation/ movies/ smoothed fields/ Mark III and mock Mark III catalogues/ voids/ links/



    The simulations have been carried out on the CRAY T3E at the Computer Center (
    RZG) of the Max-Planck Society in Garching.

    They used the parallel tree-code GADGET (Springel et al. 2001). Initially, both LCDM and TCDM simulated regions have approximatively spherical shapes and comoving radii of roughly 210 Mpc/h. They then evolve with free boundary conditions in an expanding universe. The 210 Mpc/h comoving radius includes an innermost high-resolution (hr) region, extending to 8000 km/s in radius, where the DM particles are the slightest, and an outermost low-resolution (lr) region, where the DM particles are more massive.

    Note that the galaxy formation is followed exclusively in the high-resolution region, and that we discard all high-resolution DM haloes contaminated by low-mass particles.

    • High resolution region : it extends to roughly 8000 km/s and contains low-mass particules. For each cosmology, the initial displacements and velocity fields for these particles have been contrained on scales greater than 5 Mpc/h by the IRAS 1.2 Jy survey, following the scheme of Kolatt et al. (1996). On smaller scales, additional unconstrained power (as required by the chosen cosmology) has been added up to the Nyquist frequency of the particles.

    • Low resolution region : it extends from 8000 km/s to roughly 210 Mpc/h, and contains high-mass particules. In each cosmology, the initial displacement and velocity fields for these particles have been contrained on scales greater than 5 Mpc/h by the IRAS 1.2 Jy survey. No further power has been added on smaller scales.


    We define H0=100 h km/s/Mpc. The other parameters follow standard notation.

    Cosmological parameters

    ModelOmega0Lambda hGammaSigma8

    Collisionless simulation parameters

    The subscripts "hr" and "lr" refer to the high and low resolution regions, respectively.

    N is the number of (DM) particles, M the mass (units Msun/h) of one particle, and lsoft is the physical softening length (units kpc/h).

    Model Nhr Mhr (Msun/h) lsoft,hr (kpc/h) Nlr Mlr (Msun/h) lsoft,lr (kpc/h)
    LCDM 50730389 0.357 x 1010 20 20506522 14.386 x 1010 120
    TCDM 53302154 1.18978 x 1010 20 20442823 47.952 x 1010 120

    Semi-analytic parameters

    fbar is the baryon fraction: fbar=Omegabar/Omega0

    alpha=star formation efficiency, epsilon=SNe feedback efficiency

    fbulge is the ratio of the satellite galaxy total mass to the central galaxy total mass beyond which a merger is supposed to trigger a starburst and form a bulge component

    "Feedback" gives the hypothesis that we made for the fate of the cold gas which has been reheated by the SNe (either ejected from the DM halo and later reincorporated or always retained in the halo)

    MB,lum is the luminosity resolution limit of the simulations (in the B band), defined as the mean B band magnitude of the central galaxy of a 10 particle halo at z=0.

    MB,morpho the morphology resolution limit, defined as the mean B band magnitude of the central galaxy of a 100 particle halo at z=0.

    Model fbar alpha epsilon fbulge Feedback MB,lum MB,morpho
    LCDM 0.12 0.05 0.05 0.1 retention -16.25 -18.46
    TCDM 0.2 0.15 0.03 0.1 ejection -18.45 -20.61

    Masses for Milky-Way look-alikes

    Milky Way look-alikes are defined as galaxies of type Sb/Sc with a disk circular velocity betwen 200 and 240 km/s.

    In the table below, masses are given in units of Msun, disk star formation rates in units of Msun/year, and we give our zero-point normalization of the Tully-Fisher realtion.

    Model Stellar mass Cold Gas mass disk SFR MB- 5 log h MI- 5 log h B-V Number
    LCDM 9.32 x 1010 1.05 x 1010 1.78 -20.02 -22.01 0.74 229
    TCDM 1.58 x 1011 1.15 x 1010 3.37 -20.04 -21.99 0.71 941


Some selected publications :





    More images showing specific properties of the galaxies on top of the dark matter, for the LCDM model at various redshifts are also available.


    A short movie shows the galaxy distribution on spherical shells. (caution : the movie will play at the rate of the connexion).


MarkIII and mock Mark III catalogues

Based on the results above, we ( have also constructed mock Mark III catalogues of peculiar velocities.


Constrained crealizations of the Local Universe are also ideal to study the simulated population of galaxies in voids and to evaluate to which extent semi-analytic models (to their luminosity resolution limit) successfully reproduce voids as large and as empty as the nearby ones. We have checked (
astro-ph/0201193) whether various galaxy and halo populations selected according to observationally relevant quantities could be considered to be homogeneously distributed with respect to the bright spirals.

Down to MB=-16.3, we came up wih negative conclusions for a possible homogeneous population.

Pictures are available here, and halo and galaxy catalogues used for the prospection of simulated voids can be downloaded there.

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Last modified: Feb 12, 2002. For Questions / Comments / Remarks :