"Distance mapping" and the 3-D structure of BB +30 3639
  BD +30 3639 is a member of a group of uncommon planetary nebula with
Wolf-Rayet central star and higher expansion velocities in [O III] than in [N
II] lines. Images and high-resolution spectra from the literature are used in
order to construct a 3-D model of the nebula using the morpho-kinematic code
SHAPE. We find that two homologous expansion laws are needed for the [N II] and
[O III] shell. We conclude that the internal velocity field of BD +30 3639
decreases with the distance from the central star at least between the [O III]
and [N II] shells. A cylindrical velocity component is used to replicate the
high-speed bipolar collimated outflows. We also present a new kinematic
analysis technique called "distance mapping". It uses the observed proper
motion vectors and the 3-D velocity field to generate maps that can be used as
a constraint to the morpho-kinematic modeling with SHAPE as well as improve the
accuracy for distance determination. It is applied to BD+30 3639 using 178
internal proper motion vectors from Li et al. (2002) and our 3-D velocity field
to determine a distance of 1.52 \pm 0.21 kpc. Finally, we find evidence for an
interaction between the eastern part of nebula and the ambient H2 molecular
gas.
