  The impact of three-nucleon forces (3NFs) along the oxygen chain is
investigated for the spectral distribution for attachment and removal of a
nucleon, spectroscopic factors and matter radii. We employ self-consistent
Green's function (SCGF) theory which allows a comprehensive calculation of the
single particle spectral function. For the closed subshell isotopes, $^{14}$O,
$^{16}$O, $^{22}$O, $^{24}$O and $^{28}$O, we perform calculations with the
Dyson-ADC(3) method. The remaining open shell isotopes are studied using the
newly developed Gorkov-SCGF formalism up to second order. We produce plots for
the full-fledged spectral distributions. The spectroscopic factors for the
dominant quasiparticle peaks are found to depend very little on the leading
order (NNLO) chiral 3NFs. The latters have small impact on the calculated
matter radii, which, however are consistently obtained smaller than experiment.
Similarly, single particle spectra tend to be diluted with respect to
experiment. This effect might hinder, to some extent, the onset of correlations
and screen the quenching of calculated spectroscopic factors. The most
important effects of 3NFs is thus the fine tuning of the energies for the
dominant quasiparticle states, which govern the shell evolution and the
position of driplines. Although present chiral NNLO 3NFs interactions do
reproduce the binding energies correctly in this mass region, the details of
the nuclear wave function remain at odd with the experiment showing too small
radii and a too dilute single particle spectrum, similar to what already
pointed out for larger masses. This suggests a lack of repulsion in the present
model of NN+3N interactions which is mildly apparent already for masses in the
A=14--28 range.
