Ross, N. P.; daAngela, J.; Shanks, T.; Wake, D.; Cannon, R. D.; Edge, A. C.; Nichol, R. C.; Outram, P. J.; Colless, M.; Couch, W. J.; Croom, S. M.; De Propris, R.; Drinkwater, M. J.; Eisenstein, D. J.; Loveday, J.; Pimbblet, K. A.; Roseboom, I. G.; Schneider, D. P.; Sharp, R. G. and Weilbacher, P. M.
(2007).

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DOI (Digital Object Identifier) Link:  https://doi.org/10.1111/j.13652966.2007.12289.x 

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Abstract
We present a clustering analysis of luminous red galaxies (LRGs) using nearly 9000 objects from the final, threeyear catalogue of the 2dFSDSS LRG and QSO (2SLAQ) Survey. We measure the redshiftspace twopoint 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 lineofsight velocity dispersion. We fit a double power law to ξ (s) and measure an amplitude and slope of s0 = 17.3^{+2.5} −2.0 h^{−1} Mpc, γ = 1.03 ± 0.07 at small scales (s < 4.5 h^{−1} Mpc) and s0 =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 r0 = 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 r0 = 7.45 ± 0.35 h^{−1} Mpc
and a powerlaw 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 nonpowerlaw 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 powerlaw fit to the galaxy ξ (r), under the assumption of linear bias, to model the redshiftspace distortions in the 2D redshiftspace correlation function, ξ (σ, π).We fit for the LRG velocity dispersion, wz, the density parameter, Ωm and β(z), where β(z) = Ω0.6 m /b and b is the linear bias parameter. We find values of wz = 330 km s−1,Ωm = 0.10^{+0.35} −0.10 and β = 0.40 ± 0.05. The low values for wz and β reflect the high bias of the LRG sample. These highredshift results, which incorporate the Alcock–Paczynski effect and the effects of dynamical infall, start to break the degeneracy between Ωm and β found in lowredshift 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 zLRG ∼ 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.
Item Type:  Journal Item 

Copyright Holders:  2007 The Authors, 2007 RAS 
ISSN:  00358711 
Academic Unit/School:  Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences Faculty of Science, Technology, Engineering and Mathematics (STEM) 
Item ID:  38517 
Depositing User:  Miranda Callaway 
Date Deposited:  10 Feb 2017 12:56 
Last Modified:  07 Dec 2018 14:07 
URI:  http://oro.open.ac.uk/id/eprint/38517 
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