A&A 382, 397411 (2002)
DOI: 10.1051/00046361:20011534
The cosmological constant and quintessence from a correlation function comoving fine feature in the 2dF quasar redshift survey
B. F. Roukema^{1, 2, 3}, G. A. Mamon^{4, 5} and S. Bajtlik^{6}^{1} InterUniversity Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007, India
^{2} DARC/LUTH, Observatoire de ParisMeudon, 5 place Jules Janssen, 92195 Meudon Cedex, France
^{3} University of Warsaw, Krakowskie Przedmiescie 26/28, 00927 Warsaw, Poland
^{4} Institut d'Astrophysique de Paris (CNRS UPR 341), 98bis Bd. Arago, 75014 Paris, France
email: gam@iap.fr
^{5} DAEC (CNRS UMR 8631), Observatoire de ParisMeudon, 5 place Jules Janssen, 92195 Meudon Cedex, France
^{6} Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, 00716 Warsaw, Poland
email: bajtlik@camk.edu.pl
(Received 20 June 2001 / Accepted 29 October 2001)
Abstract
Local maxima at characteristic comoving scales have previously been
claimed to exist in the density perturbation spectrum at the
wavenumber
,
where

200 (comoving), at low
redshift (
) for several classes of tracer objects, at
among quasars, and at
among Lyman break
galaxies.
Here, this cosmic standard ruler is sought in the
"10K" initial release of the 2dF QSO Redshift Survey (2QZ10K),
by estimating the spatial twopoint autocorrelation functions
of the threedimensional (comoving, spatial) distribution of
the
N=2378 quasars in the most completely observed and "covered"
sky regions of the catalogue, over the
redshift ranges
0.6 < z < 1.1 ("low
z"),
1.1 < z < 1.6 ("med
z") and
1.6 < z < 2.2 ("hi
z").
Because of the selection method of the survey and sparsity of the data,
the analysis was done conservatively to avoid noncosmological artefacts.
(i) Avoiding a priori estimates of the length scales of features,
local maxima in
are found in
all three different redshift ranges.
The requirement that
a local maximum be present in all three redshift ranges
at a fixed comoving length
scale implies strong,
purely geometric constraints on the local cosmological parameters,
in which case the length scale of the local maximum common
to the three redshift ranges is
.
(ii) For a standard cosmological constant FLRW model, the matter density
and cosmological constant are constrained to
(68% confidence),
(95% confidence),
respectively, from the 2QZ10K alone.
Independently of the type Ia supernovae data,
the zero cosmological constant model (
) is rejected at the
99.7% confidence level.
(iii) For an effective quintessence (
) model and zero curvature,
(68% confidence),
(95% confidence) are found,
again from the 2QZ10K alone.
In a different analysis of a larger (but
less complete) subset of the same 2QZ10K catalogue, Hoyle et al. (2001)
found a local maximum in the power spectrum
to exist for widely differing choices of
and
, which is difficult to understand for
a genuine large scale feature at fixed comoving length scale.
A resolution of this problem and definitive results should come from
the full 2QZ, which should clearly provide even more impressive constraints
on fine features in density perturbation statistics,
and on the local cosmological parameters
and
.
Key words: cosmology: observations  cosmology: theory  distance scale  quasars: general  largescale structure of Universe  reference systems
Offprint request: B. F. Roukema, boud.roukema@obspm.fr
© ESO 2002