MUSE spectroscopy of planetary nebulae with high abundance discrepancies
  We present MUSE deep integral-field unit spectroscopy of three planetary
nebulae(PNe) with high abundance discrepancy factors (ADF > 20): NGC 6778, M
1-42 and Hf 2-2. We have constructed flux maps for more than 40 emission lines,
and use them to build extinction, electron temperature (T$_e$), electron
density (n$_e$), and ionic abundances maps of a number of ionic species. The
effects of the contribution of recombination to the auroral [N II] and [O II]
lines on T$_e$ and the abundance maps of low-ionization species are evaluated
using recombination diagnostics. As a result, low T$_e$ values and a downward
gradient of T$_e$ are found toward the inner zones of each PN. Spatially, this
nearly coincides with the increase of abundances of heavy elements measured
using recombination lines in the inner regions of PNe, and strongly supports
the presence of two distinct gas phases: a cold and metal-rich and a warm one
with "normal" metal content. We have simultaneously constructed, for the first
time, the ADF maps of O$^+$ and O$^{2+}$ and found that they centrally peak for
all three PNe under study. We show that the main issue when trying to compute
realistic abundances from either ORLs or CELs is to estimate the relative
contribution of each gas component to the H I emission, and we present a method
to evaluate it. It is also found that, for the studied high-ADF PNe, the amount
of oxygen in the cold and warm regions is of the same order.
