**AAS 197, January 2001**

*Session 89. Large Scale Structure and Galaxy Clusters*

Oral, Wednesday, January 10, 2001, 10:30am-12:00noon, Town and Country
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## [89.04] Large-scale structure in the 2dF QSO Redshift Survey

*S. M. Croom, B. J. Boyle (AAO), T. Shanks (University of Durham), R.J. Smith (Liverpool John Moores University), L. Miller, N. S. Loaring (University of Oxford)*

We present clustering results from the 2dF QSO Redshift
Survey (2QZ), which upon completion will contain over 25000
QSOs. The current data set consists of over 15000 QSOs in
the redshift range z=0.3-2.9, so is already by far the
largest QSO sample in existence.

We measure the two-point redshift-space correlation function
of the QSOs in the 2QZ. This is shown to be a power law for
the first time. The power law extends to 35h^{-1}Mpc in an
Einstein-de-Sitter (EdS) universe. The slope and amplitude
of the power law, at a mean redshift of z=1.5, is similar
to that of local (z~.05) galaxies. For a power law of
the form \xi(s)=(s/s_{0})^{-\gamma} we find
s_{0}=4.23^{+0.33}_{-0.38}h^{-1}Mpc and
\gamma=1.50^{+0.11}_{-0.10} (EdS). A strong cosmological
constant term increases the amplitude of clustering, so that
for \lambda_{0}=0.7 and \Omega_{0}=0.3 we find
s_{0}=5.90^{+0.52}_{-0.66}h^{-1}Mpc and
\gamma=1.45^{+0.11}_{-0.09}, and the power law extends to
~0h^{-1}Mpc.

We also measure the clustering of QSOs as a function of
redshift. For an EdS universe QSO clustering is constant (in
comoving coordinates) over our entire redshift range. QSOs
thus have similar clustering properties to local galaxies at
all redshifts that we sample. In a cosmological constant
dominated universe there is a marginal increase in
clustering with increasing redshift. Although QSO clustering
is measured on large scales where linear theory should
apply, QSOs do not follow the linear theory predictions for
growth via gravitational instability. Thus a redshift
dependent QSO bias is required. Simple models based on the
Press-Schechter formalism are consistent with QSO clustering
for minimum halo masses of ~10^{12}M_{\}odot (EdS) or
~10^{13}M_{\}odot (\lambda=0.7, \Omega_{0}=0.3).

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