  The z=3.02 quasar SDSS J095253.83+011421.9 exhibits broad metal-line emission
(CIV FWHM=9000 km/s), but broad Ly-alpha emission is not present. Instead, only
a narrow Ly-alpha line is observed (FWHM=1140 km/s). The large CIV/Ly-alpha
ratio in the broad-line region (BLR) emission from this object can be matched
most closely by a BLR dominated by gas at very high densities (10^15 cm^-3),
which suppresses the Ly-alpha emission, and illuminated by an incident
power-law extending to ~200 micron, which yields increased emission from purely
collisionally excited coolant lines (such as CIV, NV and OVI) but not from
recombination lines like Ly-alpha. However, the strong CIII emission predicted
by this model is not observed, and the observed broad CIII] emission must come
from a lower-density BLR component and should be accompanied by broad Ly-alpha
emission which is not observed. The least unlikely explanation for this
spectrum seems to be that any intrinsic broad Ly-alpha emission is removed by
smooth NV absorption in the red wing of the Ly-alpha emission line and by
smooth Ly-alpha absorption in the blue wing of the Ly-alpha emission line. This
postulated smooth absorption would be in addition to the strong, associated,
narrow absorption seen in numerous ions. Smooth absorption in Ly-alpha, NV and
OVI but not in CIV would be unusual, but not impossible, although it is
suspicious that the postulated absorption must almost exactly cancel the
postulated intrinsic broad emission. We conclude that the spectrum of SDSS
J0952+0114 appears unique (among ~3600 SDSS spectra of quasars at z>2.12)
because of some_combination_ of unusual parameters, and we discuss possible
observations to determine the combination of circumstances responsible for the
spectrum.
