Constrained Simulations of the Real Universe: The Local Supercluster

Abstract

We present cosmological simulations that closely mimic the real uiverse within ~100 Mpc of the Local Group. The simulations, called constrained simulations, reproduce the large-scale density field with major nearby structures, including the Local Group, the Coma and Virgo Clusters, the Great Attractor, the Perseus-Pisces Supercluster, and the Local Supercluster, in approximately correct locations. The MARK III survey of peculiar velocities of the observed structures inside an 80 h-1 Mpc sphere is used to constrain the initial conditions. Fourier modes on scales larger than a (Gaussian) resolution of ≈Rg = 5 h-1 Mpc are dominated by the constraints, while small-scale waves are essentially random. The main aim of this paper is the structure of the Local Supercluster region (LSC; ~30 h-1 Mpc around the Virgo Cluster) and the Local Group environment. We find that at the current epoch most of the mass (≈7.5 × 1014 h-1 M☉) of the LSC is located in a filament roughly centered on the Virgo Cluster and extending over ~40 h-1 Mpc. The simulated Local Group (LG) is located in an adjacent smaller filament, which is not a part of the main body of the LSC and has a peculiar velocity of ≈250 km s-1 toward the Virgo Cluster. The peculiar velocity field in the LSC region is complicated and is drastically different from the field assumed in the Virgocentric infall models. We find that the peculiar velocity flow in the vicinity of the LG in the simulation is relatively "cold": the peculiar line-of-sight velocity dispersion within 7 h-1 Mpc of the LG is ≲60 km s-1, comparable to the observed velocity dispersion of nearby galaxies.