The z(abs)similar to z(em) absorption line systems toward QSO J 2233-606 in the Hubble Deep Field South: NeVIII lambda lambda 770,780 absorption and partial coverage

Results of a careful analysis of the highly ionized absorption systems, obs erved over the redshift range 2.198-2.2215 in the z(em) = 2.24 HDFS-QSO J 2 233-606, are presented. The strength and covering factor of the O VI and Ne VIII absorption lines suggest that the gas is closely associated with the AGN. In addition, most of the lines show signature of partial coverage and the covering factor varies from species to species. This can be understood if the clouds cover the continuum emission region completely and only a fra ction of the broad emission line region. Using photo-ionization models we analyze in more detail the component at z( abs)= 2.198, for which we can derive reliable estimates of column densities for H I and other species. Absolute abundances are close to solar but the [N/C] abundance ratio is larger than solar. This result, which is consisten t with the analysis of high-z QSO broad emission-lines, confirms the physic al association of the absorbing gas with the AGN. The observed column densi ties of N Iv, N V and Ne VIII favor a two-zone model for the absorbing regi on where Ne VIII is predominantly produced in the highly ionized zone. It i s most likely that in QSO J 2233-606, the region producing the Ne VIII abso rption can not be a warm absorber. One of the Ly alpha absorption lines at z(abs) = 2.2215 has a flat bottom t ypical of saturated lines and non-zero residual intensity in the core, cons istent with partial coverage. There is no metal-line from this Ly alpha clo ud detectable in the spectrum which suggests either large chemical inhomoge neities in the gas or that the gas is very highly ionized. If the latter is true the cloud could have a total hydrogen column density consistent with that of X-ray absorbers. It is therefore of first importance to check wheth er or not there is an X-ray warm-absorber in front of this QsO.