## 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 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 _{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, w _{p}(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, Ω _{m} 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}, Ω _{m} = 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 Ω _{m} 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 Ω _{m}(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 'high-peak' bias prescription which assumes that LRGs have a constant comoving density and their clustering evolves purely under gravity.

Original language | English (US) |
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Pages (from-to) | 573-588 |

Number of pages | 16 |

Journal | Monthly Notices of the Royal Astronomical Society |

Volume | 381 |

Issue number | 2 |

DOIs | |

State | Published - Oct 2007 |

## All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics
- Space and Planetary Science