We propose to use PHOT to carry out measurements at wavelengths of 11.5,
60 and 160um (11.5, 60, 135 and 200 for the brightest objects) of a complete
sub-sample of optically selected bright quasars taken from two recently
completed multicolour (U,B,V,R,I) quasar surveys.
The optical fluxes are in the range 15 < B < 17, partially overlapping
those of the PG survey, but with a much better photometric accuracy
(sigma_B ~ 0.1mag). Our samples show that the true surface density of
quasars in the range 15<B<16.5 is significantly higher (a factor 3) with
respect to the PG survey. No other complete quasar surveys sample such
bright fluxes. ROSAT and VLA observations have been obtained or are
going to be obtained for the whole bright sub-sample.
This programme aims at comparing the space density of optically-selected
quasars in the far-infrared (FIR) with our new estimation of the blue band
space density of these objects. This comparison will be done by means of the
first ever calculation of the bivariate luminosity function.
This will tell us how the optical-infra-red relation for quasars changes as a
function of both luminosity and redshift. Using this relation we can
derive the relative strengths of the different components responsible
for infra-red emission and disentangle the dependences on redshift and
luminosity.
Note that this project cannot be carried out by using IRAS data because of the
low sensitivity of this survey and the lack of any complete quasar
sample observed by this satellite.
Moreover, photometry at different FIR frequencies will measure the spectral
energy density distribution (S.E.D.) of the population and address the issues
of the spectral turnover and the relative importance of thermal and
non-thermal emission in the far-infrared.
30 sources will be observed in case of spring launch and the total observing
time required is ~ 15 hours, all 49 sources can be observed in case of autumn
launch with a total observing time of ~ 20 hours.