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Session 97 - Planetary Nebulae.
Display session, Thursday, January 16
Based upon spectra obtained with the MOS spectrograph at the Canada-France-Hawaii Telescope, we have derived oxygen abundances for 27 planetary nebulae in the bulge of M31. For 19 of the 21 planetary nebulae whose [O III]\lambda5007 luminosities are within 1mag of the peak of the planetary nebula luminosity function, these oxygen abundances are based upon a measured [O III]\lambda4363 intensity, so are based upon a measured electron temperature. The oxygen abundances cover a wide range, 7.85\,dex<12 + log (O/H) <9.09\,dex, but the mean abundance is surprisingly low, 12 + log (O/H) =8.64 \pm 0.32\,dex. Furthermore, the abundance distribution seems to indicate that more bright, oxygen-rich planetary nebulae do not exist in the bulge of M31.
We compare the properties of these planetary nebulae with those for bright planetary nebulae in the LMC. The distribution of the O^2+/O^+ and He\,II\,\lambda 4686/H\beta ratios for the planetary nebulae in the two galaxies are remarkably disparate. The brightest planetary nebulae in M31 have systematically larger O^2+/O^+ ratios and systematically smaller He\,II\,\lambda 4686/H\beta ratios than their LMC counterparts.
Program listing for Thursday