The Central PNe Populations of External Galaxies with SAURON
  Thanks to SAURON integral-field observations we uncovered the Planetary Nebulae (PNe) populations inhabiting the central and nuclear regions of our galactic neighbours M32 and M31, respectively, and discuss the significant differences between their corresponding PNe luminosity functions in light of the properties of their parent stellar populations. In particular, we conclude that the lack of bright PNe in the nuclear regions of M31 is likely linked to the nearly Solar value for the stellar metallicity, consistent with previous suggestions that a larger metallicity would bias the Horizontal-Branch (HB) populations toward bluer colors, with fewer red HB stars capable of producing PNe and more blue HB stars that instead could contribute to the far-UV flux that is observed in metal-rich early-type galaxies and, incidentally, also in the nucleus of M31. 
Marc Sarzi
astro-ph.CO astro-ph.SR