Planetary Nebulae in the Circumnuclear Region of M31: A Spectroscopic
  Sample
  Planetary nebulae (PNe) are an important tool for studying the dynamics and
chemical evolution of galaxies in the Local Universe, given their
characteristic, bright emission line spectra. The Andromeda Galaxy (M31)
provides a unique laboratory for studying PNe in the circumnuclear region,
thanks to its proximity and almost uniformly low line-of-sight extinction that
ensures observations with high resolution and sensitivity. Using the WIYN/Hydra
multi-fiber spectrograph, we have obtained optical (4119--6882{\AA}) spectra of
77 PN candidates selected from Hubble Space Telescope narrow-band imaging,
which are located within the central $\sim$500pc region of M31. Among these
candidates, 49 (64%) are spectroscopically observed for the first time. The
spectra of 300 previously known PNe and H II regions, which primarily reside in
the disk, are also taken for comparison. All 77 circumnuclear PN candidates
exhibit prominent emission lines, including [O III] $\lambda$5007, [N II]
$\lambda$6583, H$\alpha$ and H$\beta$, strongly suggesting that they are
genuine PNe. We measured the line fluxes, radial velocities and line widths for
all objects, and found that the radial velocities of the circumnuclear PNe
generally trace rotation of the inner bulge. We also estimated a dynamical mass
of $\sim$6.4$\pm$0.5$\times$10$^{9}$$M_{\odot}$ enclosed within an effective
galactocentric radius of 340pc, which is compatible with the previously
estimated total stellar mass in this region.
