Orbits of nearby planetary nebulae and their interaction with the
  interstellar medium
  We present and analyze the orbits of eight nearby planetary nebulae (PNs)
using two different Galactic models. The errors of the derived orbital
parameters are determined with a Monte Carlo method. Based on the derived
orbital parameters, we find that Sh 2-216, DeHt 5, NGC 7293, A21, and Ton 320
belong to the thin-disk population, and PG 1034+001 and A31 belong to the
thick-disk population. PuWe 1 probably belongs to the thick-disk population,
but its population classification is very uncertain due to the large errors of
its derived orbital parameters. The PN-ISM interactions are observed for the
eight PNs in our sample. The position angles of the proper motions of the PNs
are consistent with the directions of the PN-ISM interaction regions. The
kinematic ages of PNs are much smaller than the time for them to cross the
Galactic plane. Using the models of Borkowski et al. and Soker et al., the
PN-ISM interaction can be used to derive the local density of ISM in the
vicinity of evolved PNs. According to the three-dimensional hydrodynamic
simulations of Wareing et al. (WZO), Sh 2-216, A21, and Ton 320 are in the WZO
3 stage, PG 1034+001 and NGC 7293 are in the WZO 1 stage, and PuWe 1 is in the
WZO 2 stage.
