We propose to complete multi-wavelength photometry at 4-200 mu of a sample of
optical selected quasars from the PG survey. Only very limited data is
available from IRAS on the infrared emission from quasars: for only 24 PG
quasars did IRAS detect flux in 3 or more bands, and many of these fluxes are
only marginal and unreliable detections.  These data have been modelled in
terms of multi-component models, assuming a mixture of starburst emission and
emission from dust in the narrow-line region of the quasar, possibly in the
form of a disc (Rowan-Robinson 1994, RR94). Whilst RR94 and other workers have
shown that the AGN and starburst phenomena seem to be linked in
IRAS-detected quasars, recent observations of the host galaxies of luminous
quasars show that the profiles are consistent with being ellipticals. There
is an urgent need for good quality photometry over a wide range of
wavelengths, such as can only be provided by ISO.  These data will allow a
strong test of models for the infrared emission from quasars, will confirm
whether a starburst is indeed a common feature of quasars, and will allow
us to probe the geometry, properties and density distribution of the dust in
the narrow line region of quasars.  This in turn will provide a strong test
of unified models of AGN in which a dust disc or torus is a key feature in
explaining the range of AGN phenomena observed.
Observations of the some of the PG quasars are planned in the Central Program:
this proposal ensures that we have data for the complete sample covering all
wavelengths from 4 to 200 mu. The PG quasars are the only quasars which have
photometry from radio to x-ray and thus represent a unique sample. This is our
last chance to acquire information on these objects until FIRST flies.  Our
observations have been designed to be complementary to those of the Central
Programme for objects in common.