Ionization structure and chemical abundances of the Wolf-Rayet nebula
  NGC6888 with integral field spectroscopy
  This work aims to search for the observational footprints of the interactions
between the interstellar medium (ISM) and stellar winds in the Wolf-Rayet (WR)
nebula NGC6888 in order to understand its ionization structure, chemical
composition, and kinematics. We have collected a set of integral field
spectroscopy observations across NGC6888, obtained with PPAK in the optical
range performing both 2D and 1D analyses. Attending to the 2D analysis in the
northeast part of NGC6888, we have generated maps of the extinction structure
and electron density. We produced statistical frequency distributions of the
radial velocity and diagnostic diagrams. We have found that the spectra of a
localized region to the southwest of this pointing can be represented well by
shock models. Furthermore, we performed a thorough study of integrated spectra
in nine regions over the whole nebula. We derived electron densities ranging
from <100 to 360 cm^(-3). The electron temperature varies from ~7700 K to
~10200 K. A strong variation of up to a factor 10 between different regions in
the nitrogen abundance has been found: N/H appears lower than the solar
abundance in those positions observed at the edges and very enhanced in the
observed inner parts. Oxygen appears slightly underabundant with respect to
solar value, whereas the helium abundance is found to be above it. Finally, we
provide a scenario for the evolution of NGC6888 to explain the features
observed. This scheme consists of a structure of multiple shells.
