The Ionization State of the Halo Planetary Nebula NGC 2438
  NGC 2438 is a classical multiple shell or halo planetary nebula (PN). Its
central star and the main nebula are well studied. Also it was target of
various hydrodynamic simulations (Corradi et al. 2000). This initiated a
discussion whether the haloes are mainly containing recombined gas
(Schoenberner et al. 2002), or if they are still ionized (Armsdorfer et al.
2003). An analysis of narrow-band images and long slit spectra at multiple slit
positions was done to obtain a deeper look on morphological details and the
properties of the outer shell and halo. For this work there was data available
from ESO (direct imaging and long slit spectroscopy) and from SAAO
(spectroscopic observations using a small slit - scanning over the whole
nebula). Using temperature measurements from emission lines resulted in an
electron temperature which clearly indicates a fully ionized stage.
Additionally measurements of the electron density suggest a variation of the
filling factor.
