Model-Independent Measurements of Cosmic Expansion and Growth at z=0.57 Using the Anisotropic Clustering of CMASS Galaxies From the Sloan Digital Sky Survey Data Release 9

TL;DR

This paper presents model-independent measurements of cosmic expansion and growth at redshift 0.57 using anisotropic galaxy clustering data from SDSS DR9, achieving improved precision by modeling nonlinear effects and redshift space distortions.

Contribution

It introduces a comprehensive analysis of the 2D galaxy correlation function including nonlinear effects and RSD, providing more precise measurements of cosmological parameters at z=0.57.

Findings

Measured H(0.57)r_s(z_d)/c=0.0444 +/- 0.0019

Measured D_A(0.57)/r_s(z_d)=9.01 +/- 0.23

Measured f_g(0.57)σ_8(0.57)=0.474 +/- 0.075

Abstract

We analyze the anisotropic two dimensional galaxy correlation function (2DCF) of the CMASS galaxy sample from the Sloan Digital Sky Survey Data Release 9 (DR9) of the Baryon Oscillation Spectroscopic Survey (BOSS) data. Modeling the 2DCF fully including nonlinear effects and redshift space distortions (RSD) in the scale range of 30 to 120 h^{-1}Mpc, we find H(0.57)r_s(z_d)/c=0.0444 +/- 0.0019, D_A(0.57)/r_s(z_d)=9.01 +/- 0.23, and f_g(0.57)\sigma_8(0.57)=0.474 +/- 0.075, where r_s(z_d) is the sound horizon at the drag epoch computed using a simple integral, and f_g(z) is the growth rate at redshift z, and \sigma_8(z) represents the matter power spectrum normalization on 8h^{-1}Mpc scale at z. We find that the scales larger than 120 h^{-1}Mpc are dominated by noise in the 2DCF analysis, and that the inclusion of scales 30-40 h^{-1}Mpc significantly tightens the RSD measurement. Our measurements are consistent with previous results using the same data, but have significantly better precision since we are using all the information from the 2DCF in the scale range of 30 to 120 h^{-1}Mpc. Our measurements have been marginalized over sufficiently wide priors for the relevant parameters; they can be combined with other data to probe dark energy and gravity.