Luminosity function of planetary nebulae

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The luminosity function of planetary nebulae ( PNLF for short , from English Planetary Nebula Luminosity Function ) is a method of astronomy for determining the distance of galaxies . It is based on a universal luminosity distribution of planetary nebulae in the area of ​​the forbidden emission line  [OIII]. With the help of the PNLF, distances of up to 25 mega parsec can be determined with an accuracy of 10 percent with today's technology .

Most stars with an original mass of one to eight solar masses go through a phase as a planetary nebula before developing into a white dwarf . During this time, the nebula can very effectively convert the UV radiation from the Post-AGB star into optical radiation. Up to 15 percent of the UV radiation is emitted in the [OIII] emission line with a wavelength of 5007  Angstroms .

To determine the luminosity function of planetary nebulae in a galaxy, the galaxy is recorded with a narrow-band filter around 5007 Angstroms, then the continuum of the galaxy is recorded with a broad-band filter. All sources that can be detected in the narrow-band filter and are below the detection limit in the continuum are candidates for planetary nebulae. The candidates can also be H-II regions , supernova remnants or Lyman alpha galaxies in the background . However, these objects can be excluded as they are also strong emitters in the area of ​​other lines. As a last step, the extinction within the Milky Way and the galaxy has to be calculated.

The distribution of the brightnesses of the planetary nebulae as well as their maximum brightness does not depend on the type of galaxy , the metallicity or the age of the stars, but is universal. The independence from the metallicity arises from the fact that with a lower oxygen content the electron temperature of the plasma increases due to a lack of cooling, which leads to an increased collision rate of the ions and almost compensates for the lower density in the fog. The physics behind the age independence of the PNLF, on the other hand, is not understood, as older stars produce white dwarfs with a lower mass and lower UV luminosity.

The PNLF achieves an accuracy of 10 percent within a distance of 25 megaparsecs. If only the maximum brightness of planetary nebulae is considered, the method can also be extended to distances of 80 to 100 megaparsecs, but the error is more than doubled. Compared to the Surface Brightness Fluctuation method, the Planetary Nebula Luminosity Function systematically provides a distance that is ten percent greater.

literature

  • Magda Arnaboldi, Alessia Longobardi, Ortwin Gerhard, S. Okamura: The Planetary Nebulae Luminosity Function and distances to Virgo, Hydra I and Coma clusters . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1212.0652v1 .
  • Robin Ciardullo: The Planetary Nebula Luminosity Function at the Dawn of Gaia . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1203.5551v1 .
  • Robin Ciardullo: The Planetary Nebula Luminosity Function: Pieces of the Puzzle . In: Astrophysics. Solar and Stellar Astrophysics . 2009, arxiv : 0909.4356v1 .