A New Luminosity Function for PNe in the Large Magellanic Cloud

Abstract

A deep AAO/UKST Halpha multi-exposure stack of the LMC's central 25deg^{2} was used to uncover several thousand candidate emission line sources. Follow-up procirmatory spectroscopy by the 2dF and FLAMES multi-object spectroscopy systems on the AAT and ESO VLT led to the discovery of 460 new LMC PNe while independently recovering all 169 previously known PNe in the LMC's central area. This work is now being extended to the outer regions of the LMC through access to the Magellanic Cloud Emission Line Survey (MCELS) data where several thousand additional compact emission candidates have been found. Subsequent preliminary follow-up spectroscopy on the 2dF AAOmega system on the AAT has so far led to a further 90 new faint PNe being discovered from the first half of our observing program which aims to cover 56 deg^{2} of the outer LMC. Again all 68 previously known PNe in the region surveyed so far were independently recovered. Our new LMC planetary nebula luminosity function (PNLF) complete to 7 mag below the brightest and based on PNe within the central 25 deg^{2} region, will be extended to include the new discoveries in the outer LMC. This will provide a unique probe into the LMC's chemical and dynamical evolution. The shape of the function depends on the central star mass and on the variation of the nebula optical depth with time. This makes the overall shape of the OIII5007 PNLF an important diagnostic for galactic chemical evolution. In particular, the faint end of the function reflects core stellar evolution. For the first time we present and compare the OIII5007 PNLF corrected for foreground reddening with the same objects corrected for internal extinction.