  Recent spectroscopic observations of planetary nebulae (PNe) in several
elliptical galaxies have revealed structural and kinematical properties of the
outer stellar halo regions. In order to elucidate the origin of the properties
of these planetary nebula systems (PNSs), we consider the merger scenario in
which an elliptical galaxy is formed by merging of spiral galaxies. Using
numerical simulations, we particularly investigate radial profiles of projected
PNe number densities, rotational velocities, and velocity dispersions of PNSs
extending to the outer halo regions of elliptical galaxies formed from major
and unequal-mass merging. We find that the radial profiles of the project
number densities can be fitted to the power-law and the mean number density in
the outer halos of the ellipticals can be more than an order of magnitude
higher than that of the original spiral's halo. The PNSs are found to show a
significant amount of rotation (V/sigma >0.5) in the outer halo regions ($R$
$>$ $5R_{\rm e}$) of the ellipticals. Two-dimensional velocity fields of PNSs
are derived from the simulations and their dependences on model parameters of
galaxy merging are discussed in detail. We compare the simulated kinematics of
PNSs with that of the PNS observed in NGC 5128 and thereby discuss advantages
and disadvantages of the merger model in explaining the observed kinematics of
the PNS. We also find that the kinematics of PNSs in elliptical galaxies are
quite diverse depending on the orbital configurations of galaxy merging, the
mass ratio of merger progenitor spirals, and the viewing angle of the galaxies.
This variation translates directly into possible biases by a factor of more
than two in observational mass estimation (abridged). ~ ~
