|Constrained Realization of the Local Universe|
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Constrained Simulations of the Local Universe were made in the frame
of the GIF consortium, and involved :
1 MPA Garching
Our Constrained Realizations (CR) of the Local Universe simulate the formation and evolution of the neighbouring galaxy population starting from initial conditions with a smoothed linear density field which matches that derived from the IRAS 1.2 Jy galaxy survey. The simulations track the formation and evolution of all dark matter haloes more massive than 1011 solar masses out to a distance of 8000 km/s from the Milky Way. We have implemented prescriptions similar to those of Kauffmann et al. (1999) to follow the assembly and evolution of the galaxies within these haloes. We have focused on two variants of the CDM cosmology: a LCDM and a TCDM model. Galaxy formation in each was adjusted to reproduce the I-band Tully-Fisher relation of Giovanelli et al. (1997).
We successfully compared the present-day luminosity functions, colours, morphology and spatial distribution of our simulated galaxies with those of the real local population, in particular with the Updated Zwicky Catalogue, the IRAS PSCz redshift survey, and with individual local clusters such as Coma, Virgo and Perseus. Although some discrepancies remain, our simulations recover the observed intrinsic properties and the observed spatial distribution of the local galaxies reasonably well.
These simulations can thus be used to calibrate methods which use the
observed galaxy population to estimate the cosmic density parameter or
to draw conclusions about the mechanisms of galaxy formation. To facilitate
such work, we publically release our z=0
galaxy catalogues, together with the underlying mass distribution.
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.
We define H0=100 h km/s/Mpc. The other parameters follow standard notation.
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).
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.
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.
Please click to go to the CR data-download page, including data on the galaxy and halo void test populations.
Please click to go to the CR image page, including high resolution images, slices through simulations, slices with specific galaxy properties, and movies.
Simulating our cosmological neighbourhood: mock catalogs for velocity analysis, T. Kolatt, A. Dekel, G. Ganon and J. A. Willick, 1996, ApJ, 458, 419, astro-ph/9509066
Clustering of galaxies in a hierarchical universe -I. Methods and results at z=0, G. Kauffmann, J. Colberg, A. Diaferio and S. D. M. White, 1999, MNRAS, 303, 188, astro-ph/9805283
GADGET: A code for collisionless and gasdynamical cosmological simulations, V. Springel, N. Yoshida, S. D. M. White, New Astronomy, 2001, 6, 51, astro-ph/0003162
Simulating the Formation of the Local Galaxy Population, H. Mathis, G. Lemson, V. Springel, G. Kauffmann, S. D. M. White, A. Eldar and A. Dekel, MNRAS, submitted, astro-ph/0111099
Voids in the Simulated Local Universe, H. Mathis and S. D. M. White, MNRAS, submitted, astro-ph/0201193
Comments to: H. Mathis firstname.lastname@example.org