Disk or Halo white dwarfs ? Kinematic analysis of high proper motion surveys

We present an alternative method for the kinematic analysis of high proper motion surveys and discuss its application to the survey of Oppenheimer et al. (2001) for the selection of reliable halo white dwarfs (WDs). The local WD space density we estimate is ρWD ≃ 1 ÷ 2 · 10 −5 M⊙pc −3 , which is about an order of magnitude smaller than the value derived in Oppenheimer et al. (2001), and is consistent with the values obtained from recent reanalyses of the same data (e. Our result, which corresponds to a fraction of 0.1% ÷ 0.2% of the local dark matter, does not support the scenario suggested by the microlensing experiments that ancient cool WDs could contribute significantly to the dark halo of the Milky Way.