Journal Article

The 2dF Galaxy Redshift Survey: correlation functions, peculiar velocities and the matter density of the Universe

Ed Hawkins, Steve Maddox, Shaun Cole, Ofer Lahav, Darren S. Madgwick, Peder Norberg, John A. Peacock, Ivan K. Baldry, Carlton M. Baugh, Joss Bland-Hawthorn, Terry Bridges, Russell Cannon, Matthew Colless, Chris Collins, Warrick Couch, Gavin Dalton, Roberto de Propris, Simon P. Driver, George Efstathiou, Richard S. Ellis, Carlos S. Frenk, Karl Glazebrook, Carole Jackson, Bryn Jones, Ian Lewis, Stuart Lumsden, Will Percival, Bruce A. Peterson, Will Sutherland and Keith Taylor

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 346, issue 1, pages 78-96
Published in print November 2003 | ISSN: 0035-8711
Published online November 2003 | e-ISSN: 1365-2966 | DOI:
The 2dF Galaxy Redshift Survey: correlation functions, peculiar velocities and the matter density of the Universe

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We present a detailed analysis of the two-point correlation function, ξ(σ, π), from the 2dF Galaxy Redshift Survey (2dFGRS). The large size of the catalogue, which contains ∼220 000 redshifts, allows us to make high-precision measurements of various properties of the galaxy clustering pattern. The effective redshift at which our estimates are made is zs≈ 0.15, and similarly the effective luminosity, Ls≈ 1.4L*. We estimate the redshift-space correlation function, ξ(s), from which we measure the redshift-space clustering length, s0= 6.82 ± 0.28 h−1 Mpc. We also estimate the projected correlation function, Ξ(σ), and the real-space correlation function, ξ(r), which can be fit by a power law (r/r0), with r0= 5.05 ± 0.26 h−1 Mpc, γr= 1.67 ± 0.03. For r≳ 20 h−1 Mpc, ξ drops below a power law as, for instance, is expected in the popular Λ cold dark matter model. The ratio of amplitudes of the real- and redshift-space correlation functions on scales of 8–30 h−1 Mpc gives an estimate of the redshift-space distortion parameter β. The quadrupole moment of ξ(σ, π) on scales 30–40 h−1 Mpc provides another estimate of β. We also estimate the distribution function of pairwise peculiar velocities, ƒ(v), including rigorously the significant effect due to the infall velocities, and we find that the distribution is well fit by an exponential form. The accuracy of our ξ(σ, π) measurement is sufficient to constrain a model, which simultaneously fits the shape and amplitude of ξ(r) and the two redshift-space distortion effects parametrized by β and velocity dispersion, a. We find β= 0.49 ± 0.09 and a= 506 ± 52 km s−1, although the best-fitting values are strongly correlated. We measure the variation of the peculiar velocity dispersion with projected separation, a(σ), and find that the shape is consistent with models and simulations. This is the first time that β and ƒ(v) have been estimated from a self-consistent model of galaxy velocities. Using the constraints on bias from recent estimates, and taking account of redshift evolution, we conclude that β (L=L*, z= 0) = 0.47 ± 0.08, and that the present-day matter density of the Universe, Ωm≈ 0.3, consistent with other 2dFGRS estimates and independent analyses.

Keywords: surveys; galaxies: distances and redshifts; galaxies: statistics; cosmological parameters; large-scale structure of Universe

Journal Article.  12944 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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