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Session 81 - Planetary Nebulae.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center
We present preliminary results from a survey of the [O III] flux of galactic planetary nebulae (PN). Observations of 26 galactic PN were made during the spring of 1995. One of the goals of this survey is to construct the [O III] planetary nebula luminosity function (PNLF) for PN in our galaxy. Recent studies of extragalactic PNLF show them to be reliable yardsticks for distance determination, based on the existence of an absolute luminosity cutoff on the PNLF, which is independent of galaxy type. By observing a large population of PN in a galaxy, it becomes statistically likely that the brightest PN observed will be near this cutoff, and a distance can be derived. However, whereas all PN in a distant galaxy are considered equidistant, the approximation cannot be made for galactic sources. Further, there is considerable controversy regarding the galactic PN distance scale, with distances published differing by as much as a factor of 2. By assuming the same luminosity cutoff for the galactic PNLF as exists with extragalactic PNLF, we hope to use the galactic PNLF to provide a comparison of the various existing galactic PN distance scales. Preliminary results using one distance catalog gives an M_cutoff=-5.1, compared with an empirically determined M_cutoff=-4.5. However, we were not able to produce a recognizable PNLF due to insufficient data. Some trials with V magnitude PNLFs developed from data in the literature did produce curves consistent with the empirical [O III] PNLF. The PN distances used were gathered from published works, and our results indicate that these galactic PN distance scales show some internal validity. We will gather more data in the coming months, and attempt to refine the galactic PN distance scale using PNLFs.
Program listing for Wednesday