Constrained Local UniversE Simulations: A Local Group Factory
  Near field cosmology is practiced by studying the Local Group (LG) and its
neighbourhood. The present paper describes a framework for simulating the near
field on the computer. Assuming the LCDM model as a prior and applying the
Bayesian tools of the Wiener filter (WF) and constrained realizations of
Gaussian fields to the Cosmicflows-2 (CF2) survey of peculiar velocities,
constrained simulations of our cosmic environment are performed. The aim of
these simulations is to reproduce the LG and its local environment. Our main
result is that the LG is likely a robust outcome of the LCDM scenario when
subjected to the constraint derived from CF2 data, emerging in an environment
akin to the observed one. Three levels of criteria are used to define the
simulated LGs. At the base level, pairs of halos must obey specific isolation,
mass and separation criteria. At the second level the orbital angular momentum
and energy are constrained and on the third one the phase of the orbit is
constrained. Out of the 300 constrained simulations 146 LGs obey the first set
of criteria, 51 the second and 6 the third. The robustness of our LG factory
enables the construction of a large ensemble of simulated LGs. Suitable
candidates for high resolution hydrodynamical simulations of the LG can be
drawn from this ensemble, which can be used to perform comprehensive studies of
the formation of the LG
