The Metallicities of the Broad Emission Line Regions in the
  Nitrogen-Loudest Quasars
  We measured the metallicity Z in the broad emission line regions (BELRs) of
43 SDSS quasars with the strongest N IV] and N III] emission lines. These
N-Loud QSOs have unusually low black hole masses. We used the intensity ratio
of N lines to collisionally-excited emission lines of other heavy elements to
find metallicities in their BELR regions. We found that 7 of the 8
line-intensity ratios that we employed give roughly consistent metallicities as
measured, but that for each individual QSO their differences from the mean of
all metallicity measurements depends on the ionization potential of the ions
that form the emission lines. After correcting for this effect, the different
line-intensity ratios give metallicities that generally agree to within the
0.24 dex uncertainty in the measurements of the line-intensity ratios. The
metallicities are very high, with mean log Z for the whole sample of 5.5 Z_sun
and a maximum of 18 Z_sun. Our results argue against the possibility that the
strong N lines represent an overabundance only of N but not of all heavy
elements. They are compatible with either (1) the BELR gas has been chemically
enriched by the general stellar population in the central bulge of the host
galaxy but the Locally Optimally-emitting Cloud model used in the analysis
needs some fine tuning, or (2) that instead this gas has been enriched by
intense star formation on the very local scale of the active nucleus that has
resulted in an abundance gradient within the BELR.
