Deuterium fractionation and H2D+ evolution in turbulent and magnetized
  cloud cores
  High-mass stars are expected to form from dense prestellar cores. Their
precise formation conditions are widely discussed, including their virial
condition, which results in slow collapse for super-virial cores with strong
support by turbulence or magnetic fields, or fast collapse for sub-virial
sources. To disentangle their formation processes, measurements of the
deuterium fractions are frequently employed to approximately estimate the ages
of these cores and to obtain constraints on their dynamical evolution. We here
present 3D magneto-hydrodynamical simulations including for the first time an
accurate non-equilibrium chemical network with 21 gas-phase species plus dust
grains and 213 reactions. With this network we model the deuteration process in
fully depleted prestellar cores in great detail and determine its response to
variations in the initial conditions. We explore the dependence on the initial
gas column density, the turbulent Mach number, the mass-to-magnetic flux ratio
and the distribution of the magnetic field, as well as the initial
ortho-to-para ratio of H2. We find excellent agreement with recent observations
of deuterium fractions in quiescent sources. Our results show that deuteration
is rather efficient, even when assuming a conservative ortho-to-para ratio of 3
and highly sub-virial initial conditions, leading to large deuterium fractions
already within roughly a free-fall time. We discuss the implications of our
results and give an outlook to relevant future investigations.
