Simulations of the Local Universe Constrained by Observational Peculiar
  Velocities
  Peculiar velocities, obtained from direct distance measurements, are data of
choice to achieve constrained simulations of the Local Universe reliable down
to a scale of a few Megaparsecs. Unlike redshift surveys, peculiar velocities
are direct tracers of the underlying gravitational field as they trace both
baryonic and dark matter. This paper presents the first attempt to use solely
observational peculiar velocities to constrain cosmological simulations of the
nearby universe. In order to set up Initial Conditions, a Reverse Zel'dovich
Approximation (RZA) is used to displace constraints from their positions at z=0
to their precursors' locations at higher redshifts. An additional new feature
replaces original observed radial peculiar velocity vectors by their full 3D
reconstructions provided by the Wiener-Filter (WF) estimator. Subsequently, the
Constrained Realization of Gaussian fields technique (CR) is applied to build
various realizations of the Initial Conditions. The WF/RZA/CR method is first
tested on realistic mock catalogs built from a reference simulation similar to
the Local Universe. These mocks include errors on peculiar velocities, on
data-point positions and a large continuous zone devoid of data in order to
mimic galactic extinction. Large scale structures are recovered with a typical
accuracy of 5 Megaparsecs/h in position, the best realizations reaching a 2-3
Mpc/h precision, the limit imposed by the RZA linear theory. Then, the method
is applied to the first observational radial peculiar velocity catalog of the
project Cosmicflows. This paper is a proof of concept that the WF/RZA/CR method
can be applied to observational peculiar velocities to successfully build
constrained Initial Conditions.
