2013A&A...558A..93A

In the present paper, we discuss the classification of planetary nebulae that show interaction with the interstellar medium in terms of Galactic population. Furthermore, we investigate the case of interaction of each object in the framework of the isothermal and adiabatic shock models and we derive the mean critical, leading, and stopping densities of the nebulae located in the Galactic thin and thick disks. A sample of 34 objects with available proper motions, radial velocities, and reliable distances in the literature was used for these purposes. The results show that 16 and 10 objects are classified as Galactic thin-disk and thick-disk populations, respectively. Seven objects are classified as probable thin-disk populations, and one as a probable thick-disk population. The flow and cooling time of the post-shock nebular gas are derived and the cooling/flow time ratio shows a linear correlation versus the Galactic height of the interacting planetary nebulae. The results reveal that there is a tendency for the interacting planetary nebulae belonging to the thin disk to follow an isothermal shock model, whilst those belonging to the thick disk to follow an adiabatic shock model.