What PNe could tell about extinction inside external galaxies
Joachim Köppen
Observatoire de Strasbourg,
International Space University,
Inst.Theoret.Phys.u.Astrophysik Univers. Kiel
With the extinctions measured in the
PNe of the Galactic Bulge we had verified that the classical small
clouds model for extinction in the solar neighbourhood can easily be
generalized to the entire Galaxy. I use this model to explore the
behaviour of the individual extinctions of PNe observed in an external
galaxy. With a resonable number of objects one can determine the
opacity of the extinction disk. With a larger number would be required
to determine the ratio of the scale heights of PNe and extinction disk.
Thus the measurement of the Halpha/Hbeta intensity ratio of PNs in disk
galaxies provides a useful probe to learn about the interstellar medium
in external galaxies.