The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Growth rate of structure measurement from anisotropic clustering analysis in configuration space between redshift 0.6 and 1.1 for the Emission Line Galaxy sample (2007.09009v2)

Abstract: We present the anisotropic clustering of emission line galaxies (ELGs) from the Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 16 (DR16). Our sample is composed of 173,736 ELGs covering an area of 1170 deg$^2$ over the redshift range $0.6 \leq z \leq 1.1$. We use the Convolution Lagrangian Perturbation Theory in addition to the Gaussian Streaming Redshift-Space Distortions to model the Legendre multipoles of the anisotropic correlation function. We show that the eBOSS ELG correlation function measurement is affected by the contribution of a radial integral constraint that needs to be modelled to avoid biased results. To mitigate the effect from unknown angular systematics, we adopt a modified correlation function estimator that cancels out the angular modes from the clustering. At the effective redshift, $z_{\rm eff}=0.85$, including statistical and systematical uncertainties, we measure the linear growth rate of structure $f\sigma_8(z_{\rm eff}) = 0.35\pm0.10$, the Hubble distance $D_H(z_{\rm eff})/r_{\rm drag} = 19.1^{+1.9}_{-2.1}$ and the comoving angular diameter distance $D_M(z_{\rm eff})/r_{\rm drag} = 19.9\pm1.0$. These results are in agreement with the Fourier space analysis, leading to consensus values of: $f\sigma_8(z_{\rm eff}) = 0.315\pm0.095$, $D_H(z_{\rm eff})/r_{\rm drag} = 19.6^{+2.2}_{-2.1}$ and $D_M(z_{\rm eff})/r_{\rm drag} = 19.5\pm1.0$, consistent with $\Lambda$CDM model predictions with Planck parameters.

Overview of the Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey

This paper presents a comprehensive analysis conducted on the Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic Survey (eBOSS), focusing on Emission Line Galaxies (ELGs) within the redshift range of 0.6 to 1.1. The paper utilizes 173,736 ELGs from the survey's Data Release 16 (DR16) covering an area of 1170 square degrees to perform an anisotropic clustering analysis. The approach combines Convolution Lagrangian Perturbation Theory (CLPT) and Gaussian Streaming Redshift-Space Distortions (GS RSD) to model the Legendre multipoles of the anisotropic correlation function. A detailed modeling of radial integral constraints reveals the impact of unknown angular systematics, addressed by modifying the correlation function estimator to mitigate biased results.

Strong Numerical Results and Methodological Assertions

At the effective redshift $z_{\rm eff} = 0.85$, the research measures the linear growth rate of structure $f\sigma_8(z_{\rm eff}) = 0.35 \pm 0.10$, the Hubble distance $D_H(z_{\rm eff})/r_{\rm drag} = 19.1^{+1.9}_{-2.1}$, and the comoving angular diameter distance $D_M(z_{\rm eff})/r_{\rm drag} = 19.9 \pm 1.0$. These values align with those derived from Fourier space analysis yielding consensus values of $f\sigma_8(z_{\rm eff}) = 0.315 \pm 0.095$, $D_H(z_{\rm eff})/r_{\rm drag} = 19.6^{+2.2}_{-2.1}$, and $D_M(z_{\rm eff})/r_{\rm drag} = 19.5 \pm 1.0$. The results are consistent with the $\Lambda$CDM model predictions based on Planck parameters.

Implications for Cosmological Studies and Future Directions

This analysis provides substantial insights into cosmological parameters and the growth of large-scale structures, reinforcing the $\Lambda$CDM model and contributing to understanding dark energy and general relativity implications in cosmology. The methodological advancements in mitigating angular systematics are critical for precision studies, and the use of ELGs as cosmological tracers proves effective for extending the range of measurable redshifts, paving the way for future experiments such as DESI and Euclid.

Future developments in astrophysical surveys and models will benefit from these findings, enhancing the accuracy of cosmic expansion measurements and contributing to resolving outstanding questions about dark energy dynamics and gravity theories on a cosmological scale. The paper demonstrates how current spectroscopic methodologies can refine the map of the universe's large-scale structures, offering a standard against which new surveys can measure and interpret the cosmological constant and other variables fundamental to understanding our universe's fate.