The discrepancy between chemical abundances calculated from optical recombination lines (RLs) and collisional excitation lines (CELs) is an important unsolved problem in nebular astrophysics. In planetary nebulae (PNe) there is increasing evidence that the discrepancy is due to the presence of two gas phases: a hot component with standard metallicity, whose emission is dominated by CELs, and a much cooler plasma with a very high content of heavy elements relative to hydrogen that essentially emits in RLs. In a few tens of PNe, this discrepancy can reach very large values and has been found to be often associated with the presence of a very short-period central binary system that has undergone a common envelope phase. The coexistence of both components cannot be predicted by current mass-loss theories.

In this project we propose to determine the spatial distribution and kinematics of the emitting plasma in the RLs and CELs using integral-field spectroscopy obtained in large-aperture telescopes in order to find definitive clues to the origin of the extreme abundance discrepancies found in these objects.

This project aims to provide direct evidence for the existence of a spatially differentiated metal-rich gas phase in PNe, as well as the influence of the cold gas component in determining global PN properties, and will help to constrain the different scenarios proposed to solve this long-standing problem. The data analyzed in this project are the observational basis on which theoretical models of the evolution of both the central system and the nebula can be built.