Clustering of luminous red galaxies - IV. Baryon acoustic peak in the line-of-sight direction and a direct measurement of H(z)

Authors: Gaztañaga, Enrique; Cabré, Anna; Hui, Lam

Source: Monthly Notices of the Royal Astronomical Society, Volume 399, Number 3, November 2009 , pp. 1663-1680(18)

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Abstract:

We study the clustering of luminous red galaxies in the latest spectroscopic Sloan Digital Sky Survey data releases (DR), DR6 and DR7, which sample over 1 Gpc³ h⁻³ to z= 0.47 . The two-point correlation function ξ(σ, π) is estimated as a function of perpendicular σ and line-of-sight π (radial) directions. We find significant detection of a peak at r≃ 110 Mpc h⁻¹ , which shows as a circular ring in the σ-π plane. There is also significant evidence of a peak along the radial direction whose shape is consistent with its origination from the recombination-epoch baryon acoustic oscillations (BAO). A ξ(σ, π) model with no radial BAO peak is disfavoured at 3.2σ, whereas a model with no magnification bias is disfavoured at 2σ. The radial data enable, for the first time, a direct measurement of the Hubble parameter H(z) as a function of redshift. This is independent of earlier BAO measurements which used the spherically averaged (monopole) correlation to constrain an integral of H(z) . Using the BAO peak position as a standard ruler in the radial direction, we find H(z= 0.24) = 79.69 ± 2.32 (±1.29) km s⁻¹ Mpc⁻¹ for z= 0.15-0.30 and H(z= 0.43) = 86.45 ± 3.27 (±1.69) km s⁻¹ Mpc⁻¹ for z= 0.40-0.47 . The first error is a model-independent statistical estimation and the second accounts for systematics both in the measurements and in the model. For the full sample, z= 0.15-0.47 , we find H(z= 0.34) = 83.80 ± 2.96 (±1.59) km s⁻¹ Mpc⁻¹ .

Keywords: cosmology: observations; large-scale structure of Universe

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15405.x

Affiliations: 1: Institut de Ciències de l'Espai, IEEC-CSIC, F. de Ciències, Torre C5 par-2, Barcelona 08193, Spain

Publication date: 2009-11-01

Clustering of luminous red galaxies - IV. Baryon acoustic peak in the line-of-sight direction and a direct measurement of H(z)

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