postscript
5 Distant clusters...
Abstract...
References...
A CMB decrement of 
has been observed by the
Ryle Telescope towards the pair of quasars PC1643+4631 A & B at red-shift
separated by 100 arc-seconds (Jones et al. (1997)). Assuming a
Sunyaev--Zel'dovich effect from a cluster of galaxies, this is indicative of a
rich intervening cluster of total mass 
,
although, no X-ray cluster has yet been observed in that direction. This
suggests that the object is lying at a red-shift greater than one. The quasars'
spectra analysis reveals that they might be originating from a unique source
lensed by the distant cluster (Saunders et al. (1997)).
Using our model, we are able to fit those observations and retrieve the S--Z
flux decrement as well as the 100 arc-seconds separation. To do so, we have to
consider the cluster described in section 5 with an electron
temperature of 
, which corresponds to a rich but rather
cool cluster. As we stated in section 5.1, the resulting
Rees--Sciama temperature decrement is 
which is a
considerable fraction of the S--Z decrement, here 
.
Fitting those data is of great importance since such a distant lensed-pair has
previously never been observed. As the cluster lies at a rather large
red-shift, we believe that a model such as ours, computing rigorously both the
cluster and the universe evolutions, is needed.