[Paper Review] The Completed SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: Growth rate of structure measurement from cosmic voids

M Aubert, Marie-Claude Cousinou+20 more|arXiv (Cornell University)|Jul 17, 2020

Cosmology and Gravitation Theories111 references49 citations

TL;DR

This paper presents the first growth rate of structure measurements from cosmic voids using the completed SDSS-IV eBOSS DR16 survey, employing redshift-space distortions in void-galaxy cross-correlations to constrain the growth rate. It reports fσ8 = 0.50 ± 0.11 at z=0.74 (LRG+CMASS), fσ8 = 0.52 ± 0.10 at z=0.85 (ELG), and fσ8 = 0.30 ± 0.13 at z=1.48 (QSO), consistent with conventional clustering methods and demonstrating voids as a competitive probe of cosmic structure growth.

ABSTRACT

We present a void clustering analysis in configuration-space using the completed Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic Survey (eBOSS) DR16 samples. These samples consist of Luminous Red Galaxies (LRG) combined with the high redshift tail of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) DR12 CMASS galaxies (called as LRG+CMASS sample), Emission Line Galaxies (ELG) and quasars (QSO). We build void catalogues from the three eBOSS DR16 samples using a ZOBOV-based algorithm, providing 2,814 voids, 1,801 voids and 4,347 voids in the LRG+CMASS, ELG and QSO samples, respectively, spanning the redshift range $0.6<z<2.2$. We measure the redshift space distortions (RSD) around voids using the anisotropic void-galaxy cross-correlation function and we extract the distortion parameter $\beta$. We test the methodology on realistic simulations before applying it to the data, and we investigate all our systematic errors on these mocks. We find $\beta^{ m LRG}(z=0.74)=0.415\pm0.087$, $\beta^{ m ELG}(z=0.85)=0.665\pm0.125$ and $\beta^{ m QSO}(z=1.48)=0.313\pm0.134$, for the LRG+CMASS, ELG and QSO sample, respectively. The quoted errors include systematic and statistical contributions. In order to convert our measurements in terms of the growth rate $f\sigma_8$, we use consensus values of linear bias from the eBOSS DR16 companion papers~\citep{eBOSScosmo}, resulting in the following constraints: $f\sigma_8(z=0.74)=0.50\pm0.11$, $f\sigma_8(z=0.85)=0.52\pm0.10$ and $f\sigma_8(z=1.48)=0.30\pm0.13$. Our measurements are consistent with other measurements from eBOSS DR16 using conventional clustering techniques.

Motivation & Objective

• To measure the growth rate of cosmic structure using cosmic voids as a probe in the completed eBOSS DR16 survey.
• To test the robustness of void-based redshift-space distortion (RSD) analysis against systematic errors using realistic N-body simulations.
• To provide independent constraints on fσ8 using void-galaxy cross-correlation functions, complementing traditional galaxy clustering techniques.
• To demonstrate the viability of voids as a competitive cosmological probe in large-scale structure surveys, especially with upcoming high-precision surveys.

Proposed method

• Constructed void catalogues from eBOSS DR16 samples (LRG+CMASS, ELG, QSO) using the ZOBOV algorithm, identifying 2,814, 1,801, and 4,347 voids respectively across 0.6 < z < 2.2.
• Measured the anisotropic void-galaxy cross-correlation function in configuration space to extract redshift-space distortions (RSD) and the distortion parameter β.
• Applied a linear RSD model (Cai et al. 2016) to relate β to the growth rate, with systematic errors tested on realistic N-body simulations.
• Calibrated the linear bias using consensus values from eBOSS DR16 companion papers to convert β into fσ8 measurements.
• Quantified systematic uncertainties from void finding, geometry, and density field reconstruction, validating the method on mock surveys.
• Combined results across three tracers (LRG+CMASS, ELG, QSO) to provide redshift-dependent constraints on fσ8.

Experimental results

Research questions

• RQ1 Can cosmic voids provide competitive constraints on the growth rate of structure fσ8 when analyzed via redshift-space distortions in the void-galaxy cross-correlation function?
• RQ2 How do systematic errors in void finding and density field reconstruction affect the measured growth rate, and can they be reliably quantified?
• RQ3 Are the fσ8 measurements from voids consistent with those obtained using standard galaxy clustering techniques in the same eBOSS DR16 dataset?
• RQ4 Do void-based measurements show sensitivity to structure growth in low-density regions, offering a complementary test to galaxy clustering in overdense regions?
• RQ5 Can voids serve as a robust cosmological probe in future surveys like DESI and Euclid, given the expected increase in void counts and reduced statistical errors?

Key findings

• The measured distortion parameter is β(LRG+CMASS, z=0.74) = 0.415 ± 0.087, β(ELG, z=0.85) = 0.665 ± 0.125, and β(QSO, z=1.48) = 0.313 ± 0.134, with errors combining statistical and systematic contributions.
• After converting β to fσ8 using consensus linear bias values from eBOSS DR16 companion papers, the constraints are fσ8(z=0.74) = 0.50 ± 0.11, fσ8(z=0.85) = 0.52 ± 0.10, and fσ8(z=1.48) = 0.30 ± 0.13.
• The void-based fσ8 measurements are consistent with those derived from conventional galaxy clustering in the same eBOSS DR16 dataset.
• The improved statistics in DR16—2,814 voids in LRG+CMASS and 4,347 in QSO samples—represent a significant increase over DR14, enhancing precision and reducing statistical uncertainty.
• The method successfully controls systematic errors through validation on realistic simulations, confirming robustness for cosmological inference.
• The results confirm that cosmic voids are a viable and complementary probe for measuring the growth rate of structure, especially in low-density regions, and are well-suited for next-generation surveys.