One of the great advances in our understanding of the active galactic
nucleus phenomenon in recent years has been the development of the
Standard Model for unification of broad and narrow-lined objects.
Although apparently very different, the idea has arisen that narrow
line objects (e.g. Seyfert 2s, narrow-line radiogalaxies) are
intrinsically the same as their broad line counterparts, but with
the nuclear continuum source and broad line region (BLR) obscured
from direct view by a dusty molecular torus. The observational
evidence for this scenario is quite diverse, comprising strong
near-infrared emission from narrow-line objects, depolarization of
radio lobes and spectropolarimetry (see Antonucci 1993 for a recent
review).

The observational signature of hot dust at the inner wall of the
torus is thermal radiation at 1500-2000 K (the dust sublimation
temperature) and this is seen in low-redshift quasars, where the
luminosity of the central source is such that it must be located at
a radial distance of approximately 1 parsec. For much more luminous
sources at higher redshift, the inner wall cannot be at a distance
of less than 10 parsecs, which is comparable to the predicted overall
size of the torus; this therefore suggests that tori may not exist in
these objects at all, and the thermal bump may be absent from their
spectra. We propose to investigate this idea be obtaining low
resolution spectra of the wavelength region of the redshifted bump
(which is inaccessible from the ground) and hence determine whether
or not it still exists in high luminosity/redshift quasars. This
will allow us to place constraints on the physical size and
structure of the region. Also, it will test an important tenet
of unified schemes which claim that dusty nuclear regions are less
important in the higher luminosity quasars.