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The Galaxy Environment of QSOs in Large Quasar Groups
C.P. Haines et al.
University of Central Lancashire, U.K.
Quasars have been used as eфcient probes of high-redshift cluster-
ing on the basis that they are known to favour rich environments.
Quasars may also trace the large-scale structure of the early uni-
verse (0:4  z  2) in the form of Large Quasar Groups (LQGs),
which have comparable sizes (100{200h 1 Mpc) to those of the
largest structures seen at the present epoch.
We are investigating the galaxy environment of the Clowes &
Campusano (MNRAS 249, 218 [1991]) LQG of 18 QSOs at z ' 1:3,
by combining ultra-deep optical images (to V ' 27; I ' 26) of a
30 0  30 0 eld containing 3 of the LQG quasaars with NIR imag-
ing (K ' 20) of selected subelds to obtain photometric redshift
estimates for each galaxy from their V IK colours.
In a 2:25 0  2:25 0 eld centred on the z=1.226 quasar
J1046.9+0541, signicant clustering is observed with 15{18 galax-
ies with the colours (I K ' 4:3; V K ' 6:9) and magnitudes
expected for massive ellipticals at the quasar redshift (Haines et
al., MNRAS submitted [2000]). These galaxies are concentrated
in two compact groups 90 00 apart, which are bisected by a band
of blue galaxies where the quasar is located. This spatial dis-
tribution suggests that the two groups are merging and that the
interaction of galaxies with shocks in the ICM has triggered the
band of enhanced star-formation and also the quasar.
Co-authors: R.G. Clowes/University of Central Lancashire, UK.,
L.E. Campusano/Universidad de Chile, Chile
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