## Abstract

We present a clustering analysis of luminous red galaxies (LRGs) using nearly 9000 objects
from the final, three-year catalogue of the 2dF-SDSS LRG and QSO (2SLAQ) Survey. We
measure the redshift-space two-point correlation function, ξ (s) and find that, at the mean LRG
redshift of ¯z = 0.55, ξ(s) shows the characteristic downturn at small scales (1 h−1 Mpc)
expected from line-of-sight velocity dispersion.We fit a double power law to ξ (s) and measure
an amplitude and slope of s

We use the simple power-law fit to the galaxy ξ (r), under the assumption of linear bias, to model the redshift-space distortions in the 2D redshift-space correlation function, ξ (σ, π).We fit for the LRG velocity dispersion, w

_{0}= 17.3^{+2.5}_{−2.0}h^{−1}Mpc, γ = 1.03 ± 0.07 at small scales (s < 4.5 h^{−1}Mpc) and s_{0}=9.40±0.19 h^{−1}Mpc, γ =2.02±0.07 at large scales (s>4.5 h^{−1}Mpc). In the semiprojected correlation function, wp(σ), we find a simple power law with γ = 1.83 ± 0.05 and r_{0}= 7.30 ± 0.34 h^{−1}Mpc fits the data in the range 0.4 < σ <50 h^{−1}Mpc, although there is evidence of a steeper power law at smaller scales. A single power law also fits the deprojected correlation function ξ (r), with a correlation length of r_{0 }= 7.45 ± 0.35 h^{−1}Mpc and a power-law slope of γ = 1.72 ± 0.06 in the 0.4 < r < 50 h^{−1}Mpc range. But it is in the LRG angular correlation function that the strongest evidence for non-power-law features is found where a slope of γ =−2.17 ± 0.07 is seen at 1 < r < 10 h^{−1}Mpc with a flatter γ = −1.67 ± 0.07 slope apparent at r 1 h^{−1}Mpc scales.We use the simple power-law fit to the galaxy ξ (r), under the assumption of linear bias, to model the redshift-space distortions in the 2D redshift-space correlation function, ξ (σ, π).We fit for the LRG velocity dispersion, w

_{z}, the density parameter, Ωm and β(z), where β(z) = Ω^{0.6}_{m}/b and b is the linear bias parameter. We find values of w_{z}= 330 km s^{−1}, Ωm = 0.10^{+0.35}_{−0.10}and β = 0.40 ± 0.05. The low values for w_{z }and β reflect the high bias of the LRG sample. These high-redshift results, which incorporate the Alcock–Paczynski effect and the effects of dynamical infall, start to break the degeneracy between Ωm and β found in low-redshift galaxy surveys such as 2dFGRS. This degeneracy is further broken by introducing an additional external constraint, which is the value β(z = 0.1) = 0.45 from 2dFGRS, and then considering the evolution of clustering from z ∼ 0 to z_{LRG}∼ 0.55. With these combined methods we find Ωm(z = 0) = 0.30 ± 0.15 and β(z = 0.55) = 0.45 ± 0.05. Assuming these values, we find a value for b(z = 0.55) = 1.66 ± 0.35. We show that this is consistent with a simple ‘highpeak’ bias prescription which assumes that LRGs have a constant comoving density and their clustering evolves purely under gravity.Original language | English |
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Pages (from-to) | 573-588 |

Journal | Monthly Notices of the Royal Astronomical Society |

Volume | 381 |

Issue number | 2 |

Early online date | 21 Oct 2007 |

DOIs | |

Publication status | Published - 2007 |