TY - JOUR
T1 - The 2dF-SDSS LRG and QSO Survey
T2 - The LRG 2-point correlation function and redshift-space distortions
AU - Ross, Nicholas P.
AU - Da Ângela, J.
AU - Shanks, T.
AU - Wake, David A.
AU - Cannon, Russell D.
AU - Edge, A. C.
AU - Nichol, R. C.
AU - Outram, P. J.
AU - Colless, Matthew
AU - Couch, Warrick J.
AU - Croom, Scott M.
AU - De Propris, Roberto
AU - Drinkwater, Michael J.
AU - Eisenstein, Daniel J.
AU - Loveday, Jon
AU - Pimbblet, Kevin A.
AU - Roseboom, Isaac G.
AU - Schneider, Donald P.
AU - Sharp, Robert G.
AU - Weilbacher, P. M.
PY - 2007/10
Y1 - 2007/10
N2 - 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 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, w p(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 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, wz, the density parameter, Ωm and β(z), where β(z) = Ω0.6m/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 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 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 'high-peak' bias prescription which assumes that LRGs have a constant comoving density and their clustering evolves purely under gravity.
AB - 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 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, w p(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 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, wz, the density parameter, Ωm and β(z), where β(z) = Ω0.6m/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 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 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 'high-peak' bias prescription which assumes that LRGs have a constant comoving density and their clustering evolves purely under gravity.
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U2 - 10.1111/j.1365-2966.2007.12289.x
DO - 10.1111/j.1365-2966.2007.12289.x
M3 - Article
AN - SCOPUS:35148882450
SN - 0035-8711
VL - 381
SP - 573
EP - 588
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -