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Planetary nebulae (PNs) are the only test particles which can provide kinematic information about all three stellar components of a spiral galaxy: the bulge, disk and halo. Kinematic information about the old stellar population in the bulge and disk usually comes from integrated absorption spectra. The rapid fall off in the surface brightness limits such observation to the very central region of M~31. Little is known about the dynamics of the old stellar disk and the stellar halo. However, in a previous work, Nolthenius and Ford detected 37 PNs in M31 between 15 and 30 kpc. They showed that while the disk PNs at $\sim$ 20 kpc have a rotation velocity 20 km/s slower than the HI, their limited data suggested that the halo PNs are dynamically similar to the halo globular clusters.
We have greatly improved and extended the early work by obtaining 1000 new PN spectra with the Hydra Multifiber Spectrograph on the KPNO 4-m telescope. The new PN data provide a spatially complete and kinematically unbiased sample in a 40 kpc by 20 kpc region centered on M~31. The observed PNs will be statistically separated into the disk, bulge and halo populations based on their kinematics. This paper reports on the preliminary results of a comprehensive study on the dynamics of the M~31 planetary nebula system.
