Cosmicflows Constrained Local UniversE Simulations
  This paper combines observational datasets and cosmological simulations to
generate realistic numerical replicas of the nearby Universe. These latter are
excellent laboratories for studies of the non-linear process of structure
formation in our neighborhood. With measurements of radial peculiar velocities
in the Local Universe (cosmicflows-2) and a newly developed technique, we
produce Constrained Local UniversE Simulations (CLUES). To assess the quality
of these constrained simulations, we compare them with random simulations as
well as with local observations. The cosmic variance, defined as the mean
one-sigma scatter of cell-to-cell comparison between two fields, is
significantly smaller for the constrained simulations than for the random
simulations. Within the inner part of the box where most of the constraints
are, the scatter is smaller by a factor 2 to 3 on a 5 Mpc/h scale with respect
to that found for random simulations. This one-sigma scatter obtained when
comparing the simulated and the observation-reconstructed velocity fields is
only 104 +/- 4 km/s i.e. the linear theory threshold. These two results
demonstrate that these simulations are in agreement with each other and with
the observations of our neighborhood. For the first time, simulations
constrained with observational radial peculiar velocities resemble the Local
Universe up to a distance of 150 Mpc/h on a scale of a few tens of megaparsecs.
When focusing on the inner part of the box, the resemblance with our cosmic
neighborhood extends to a few megaparsecs (< 5 Mpc/h). The simulations provide
a proper Large Scale environment for studies of the formation of nearby
objects.
