First Constraints on Growth Rate from Redshift-Space Ellipticity Correlations of SDSS Galaxies at $0.16 < z < 0.70$

TL;DR

This study presents the first constraints on the universe's growth rate using galaxy intrinsic alignments from SDSS data, demonstrating that combining IA statistics with galaxy clustering improves measurement precision and aligns with general relativity predictions.

Contribution

It introduces a novel method of constraining the growth rate by incorporating intrinsic alignment measurements with galaxy clustering data, enhancing accuracy over traditional approaches.

Findings

Measured IA correlations over $0.16 < z < 0.7$ from SDSS and BOSS data.

Achieved a 19% improvement in constraining $f\sigma_8$ by combining IA with clustering.

Results are consistent with general relativity predictions at $z=0.34$.

Abstract

We report the first constraints on the growth rate of the universe, $f(z)\sigma_8(z)$, with intrinsic alignments (IAs) of galaxies. We measure the galaxy density-intrinsic ellipticity cross-correlation and intrinsic ellipticity autocorrelation functions over $0.16 < z < 0.7$ from luminous red galaxies (LRGs) and LOWZ and CMASS galaxy samples in the Sloan Digital Sky Survey (SDSS) and SDSS-III BOSS survey. We detect clear anisotropic signals of IA due to redshift-space distortions. By combining measured IA statistics with the conventional galaxy clustering statistics, we obtain tighter constraints on the growth rate. The improvement is particularly prominent for the LRG, which is the brightest galaxy sample and known to be strongly aligned with underlying dark matter distribution; using the measurements on scales above $10\,h^{-1}\,{\rm Mpc}$, we obtain $f\sigma_8 = 0.5196^{ + 0.0352}_{ - 0.0354}$ (68\% confidence level) from the clustering-only analysis and $f\sigma_8 = 0.5322^{ + 0.0293}_{ - 0.0291}$ with clustering and IA, meaning $19\%$ improvement. The constraint is in good agreement with the prediction of general relativity, $f\sigma_8 = 0.4937 $ at $z=0.34$. For LOWZ and CMASS samples, the improvement of constraints on $f\sigma_8$ is found to be $10\%$ and $3.5\%$, respectively. Our results indicate that the contribution from IA statistics for cosmological constraints can be further enhanced by carefully selecting galaxies for a shape sample.