Spectroscopic Investigations of Halos of Planetary Nebulae

Extract

Different ESO-telescopes with medium resolution spectrographs and CCD-detectors were used to look for emission from extended halos around Planetary Nebulae. In three out of four cases the search was successful. The ratio R_halo/R_neb ranges from 2 to about 10. Assuming that the halos have been produced by the winds of the Red Giant progenitor stars, we determine Ṁ/V_AGB of these progenitors, using the measured Hα- and Hβ-fluxes. These values scatter in a relatively narrow range around 2‥5 · 10⁻⁷ (M⊙/y)/(km/s). In some objects emission line fluxes were measured at two ore more radial distances and radial density profiles were derived from them. These are in good agreement with the expected n∼r⁻² density law expected for a freely expanding wind.