Planetary Nebulae In The Circumnuclear Region Of M31:Identification And Spectroscopic Observation

Understanding the circumnuclear region of galaxies is crucial for the study of galaxy formation and evolution.Thanks to its proximity and low line-of-sight ex-tinction that ensure observations with high resolution and sensitivity,M31 provides a unique laboratory for studying the circumnuclear region.With its wide distribution and strong emission lines,planetary nebulae(PNe)become an important tool for studying the dynamics and chemical evolution of galaxies in the local Universe.By contrasting narrow band images from HST/WFC3 filter F502N and F547M,we found 249 PNe can-didates,which are located within the central?500 pc region of M31,and obtained their m5007.Using the WIYN/Hydra multi-fiber spectrograph,we obtained optical(4119-6882 A)spectra of 77 PN candidates.The spectra of 300 previously known PNe and HII regions,which primarily reside in the disk,are also taken for comparison.All 77 cir-cumnuclear PN candidates exhibit prominent emission lines,especially[O ?]?5007,strongly suggesting that they are genuine PNe.We derive and present line intensities,radial velocities and line widths for all objects.We find that the radial velocities of the circumnuclear PNe trace rotation of the inner bulge.We also estimate a dynamical mass of(6W±0.5)×109 M? enclosed within an effective deprojected galactocetric radius of 340 pc,which is compatible with previously estimated stellar mass in this region.In the end,we report a 2D spectroscopic observation in the circumnuclear region of M31 and measured the emission lines'(which trace the diffuse ionized gas)fluxes and radial velocities.We presented map of emission lines as well as their BPT diagram.