Densities, temperatures, pressures, and abundances derived from OII
  recombination lines in HII regions and their implications
  Based on high quality observations of multiplet V1 of OII and the NLTE atomic
computations of OII we study the density and temperature of a sample of HII
regions. We find that the signature for oxygen rich clumps of high density and
low temperature is absent in all objects of our sample: one extragalactic and
eight Galactic HII regions. The temperatures derived from: a) recombination
lines of OII, and b) recombination lines of HI together with Balmer continua
are lower than those derived from forbidden lines, while the densities derived
from recombination lines of OII are similar or smaller than densities derived
from forbidden lines. Electron pressures derived from collisionally excited
lines are about two times larger than those derived from recombination lines.
These results imply that the proper abundances are those derived from
recombination lines and suggest that other processes in addition to direct
photoionization, such as dissipation of turbulent energy in shocks, magnetic
reconnection, and shadowed regions, might be responsible for the large ADF and
t2 values observed in HII regions.
