Annu. Rev. Astron. Astrophys. 1999. 37: 487-531
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4. GENERAL ABUNDANCE SUMMARY

The main abundance results are as follows.

  1. There is a growing consensus from the BELs and NALs for Z gtapprox Zodot in QSOs out to z > 4. The upper limits on the metallicities are not well known, but none of the data require Z > 10 Zodot. 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.
  2. A trend in the NV/HeII and NV/CIV BEL ratios suggests that the metallicities are generally higher in more luminous QSOs.
  3. 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 Z gtapprox Zodot (because of the likely secondary origin of nitrogen at these metallicities).
  4. 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.
  5. 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in P and other odd-numbered elements like Al (Shields 1996)] are inconsistent with observed BEL spectra (based on unpublished work in collaboration with G Shields).

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