Physical and chemical properties of Wolf-Rayet planetary nebulae
  Wolf-Rayet ([WR]) and weak emission-line ($wels$) central stars of planetary
nebulae (PNe) have hydrogen-deficient atmospheres, whose origins are not well
understood. In the present study, we have conducted plasma diagnostics and
abundance analyses of 18 Galactic PNe surrounding [WR] and $wels$ nuclei, using
collisionally excited lines (CELs) and optical recombination lines (ORLs)
measured with the Wide Field Spectrograph on the ANU 2.3-m telescope at the
Siding Spring Observatory complemented with optical archival data. Our plasma
diagnostics imply that the electron densities and temperatures derived from
CELs are correlated with the intrinsic nebular H$\beta$ surface brightness and
excitation class, respectively. Self-consistent plasma diagnostics of heavy
element ORLs of N${}^{2+}$ and O${}^{2+}$ suggest that a small fraction of cool
($\lesssim 7000$ K), dense ($\sim 10^4-10^5$ cm$^{-3}$) materials may be
present in some objects, though with large uncertainties. Our abundance
analyses indicate that the abundance discrepancy factors (ADF$\equiv$ORLs/CELs)
of O${}^{2+}$ are correlated with the dichotomies between forbidden-line and He
I temperatures. Our results likely point to the presence of a tiny fraction of
cool, oxygen-rich dense clumps within the diffuse warm ionized nebulae.
Moreover, our elemental abundances derived from CELs are mostly consistent with
AGB models in the range of initial masses from 1.5 to 5M$_{\odot}$. Further
studies are necessary to understand better the origins of abundance
discrepancies in PNe around [WR] and $wels$ stars.
