1 Introduction

With this work we present six new planetary nebulae (PNe) in the southern hemisphere. The candidates have been taken from an internal list and complement 12 PNe from the northern hemisphere published recently (Kerber et al. 1996, hereafter Paper I). The objects were discovered by scanning the ESO/SERC survey plates for extended nebulae of low surface brightness, see e.g. Melmer & Weinberger (1990) for details of the search method; the area covered by the search represents about 40% of the southern sky.
The importance of the late stages of PN evolution and the interesting finds made over recent years have been described in Paper I; we will not repeat this here. Instead we will concentrate on one aspect, briefly mentioned in Paper I that seems to be highly relevant for some of the objects presented here. The process in point is the interaction of old evolved PNe with the surrounding ambient interstellar medium (ISM). Although first studied 20 years ago (Smith 1976) it remained somewhat of a curiosity, seemingly applicable only to a few peculiar objects like e.g. A35 (Jacoby 1981; Hollis et al. 1996). Only with the work of Borkowski et al. (1990) it became obvious that such an interaction is of importance for many old, evolved objects. Since then a number of examples ranging from the mild e.g. A34 (Tweedy & Kwitter 1994) to the extreme of Sh2-174 (Tweedy & Napiwotzki 1994) have been identified. Most recently Xilouris et al. (1996) have considerably enlarged the sample of known examples.

The objects presented in this paper nicely demonstrate first that many more galactic PNe can be discovered and second that, as a consequence of the high degree of individuality that is inherent to PNe, every single object is of interest and well worth studying.

The objects discussed here are newly discovered PNe. They are included in the first supplement to the Strasbourg-ESO-Catalogue, by Acker et al. (1996), as private communication. With the spectra and images presented in this article we are able to discuss these nebulae on a more solid basis.