Planetary Nebulae as Distance Indicators.
Planetary Nebulae as Distance Indicators
The planetary
nebula luminosity function (PNLF) is one of the most accurate tools
for measuring extragalactic distances. By taking an image of a galaxy
through a narrow-band filter centered on the emission line of doubly
ionized oxygen at 5007 A, and subtracting a similar image taken
just off the line, large samples of PN can be identified in galaxies
out to the Virgo Cluster. The luminosity function of these PN is an
excellent standard candle.
The PNLF method was originally used in elliptical and S0
galaxies, where the problems presented by internal extinction and
interloping H II regions are minimal. However, the technique works
just as well on spiral galaxies, and now over a dozen late-type
systems have been measured. Consequently, PNLF measurements are the
most direct way of connecting the Pop I and Pop II distance ladders.
For further information check out our
- Schematic
of where the PNLF method fits into the distance ladder .
-
Publications based on PNLF measurements.
Web page by Robin Ciardullo ( rbc@astro.psu.edu )
Department of Astronomy and Astrophysics
Penn State University