In March 1986, Steidel and I obtained spectra (~ 2 Å resolution,
S/N ratio ~
40) at the Las Campanas Observatory of two QSOs, Tol1037-2704
(zem = 2.193) and
Tol1038-2712 (zem = 2.331), to
which attention had been drawn by
Jakobsen et
al. (1986).
The QSOs are separated by 17.9 arcmin on the sky. Confirming and
extending
the work of Jakobsen et al., it was found that there are at least
five absorption systems
in the spectrum of each QSO, occupying the same narrow range in redshift
from 1.89
to 2.14. There is a statistically significant excess of absorption
systems in the spectra
of both QSOs; however, the tendency which was pointed out by Jakobsen
et al. for
the systems in one QSO to match a corresponding system in the other to
within 1800 km s-1 was judged not to be significant
(Sargent and
Steidel 1987).
For a Universe
with q0 = 0.5, the separation of the two lines of
sight is ~ 4.3 h100 Mpc, by far the
largest distance over which correlated absorption has ever been seen. In
addition,
we obtained low-resolution (~ 4 Å) spectra of a fainter QSO
Tol1038-2707 (only 5
arcmin from Tol1038-2712) which has a strong absorption system
(zabs 
1.887) which
corresponds to one of the common absorption systems in the other two QSO
spectra,
as well as a spectrum of Tol1037-2742 containing a possible strong
absorption system
at z ~ 1.86. In April 1987, another nearby QSO, Tol1035-2737, was
found to have a
redshift of zem = 2.168 and to have absorption
redshifts at zabs = 2.125, 2.040 and
1.905, respectively. Collectively, these observations suggest that this
general direction
in the sky contains a large supercluster extending from a redshift of
around z = 2.14 to
1.86. Tol1038-2712 lies behind the supercluster,
Tol1037-2704 and
Tol1035-2737 lie at
its most distant edge, while Tol1038-2707 is close to the nearer
edge. The supercluster
has an extent along the line of sight of ~ 50 Mpc at the epoch
corresponding to z ~ 2.
Its boundaries on the plane of the sky are not known as yet; however,
the extent in this
direction is at least 10 Mpc. Such extended structures, if elongated,
would produce
a non-Poissonian distribution of number of absorption redshifts per QSO
of the kind referred to in the discussion of the results of the CIV survey.