There is a growing consensus from the BELs and NALs
for ZZ in
QSOs out to z > 4. The upper limits on the
metallicities are not well known, but none of the data
require Z > 10
Z. Solar
to a few times solar metallicity appears to be typical. Based on very
limited data, there is no evidence for a decline at the highest
redshifts.
A trend in the NV/HeII and NV/CIV BEL ratios suggests
that the metallicities are generally higher in more luminous QSOs.
The BELs and NALs both suggest that the relative nitrogen abundance
(e.g. N/C and N/O) is typically solar or higher. We will argue below
(Section 6) that this result corroborates the
evidence for ZZ
(because of the likely secondary origin of nitrogen at these
metallicities).
There is tentative evidence for super-solar Fe/Mg abundances out
to z > 4 based on the FeII/MgII BEL strengths. Again, based on
limited data, there is no evidence for a decline in this ratio at
the highest redshifts.
The extremely high metallicities and large P/C ratios derived so far
from the BALs are probably incorrect. In further support of that
conclusion, we note that BELR simulations with the nominally derived BAL
abundances [including large enhancements in P and other odd-numbered
elements like Al
(Shields 1996)]
are inconsistent with observed BEL
spectra (based on unpublished work in collaboration with G
Shields).