[Paper Review] Measurements of cosmic expansion and growth rate of structure from voids in the Sloan Digital Sky Survey between redshift 0.07 and 1.0

Alex Woodfinden, S. Nadathur+4 more|arXiv (Cornell University)|May 12, 2022

Galaxies: Formation, Evolution, PhenomenaPhysics and Astronomy71 references42 citations

TL;DR

This study measures cosmic expansion and structure growth using void-galaxy cross-correlations in Sloan Digital Sky Survey data (z = 0.07–1.0), applying redshift-space reconstruction to reduce selection biases. It achieves higher precision for the distance ratio 𝐷M/𝐷H than BAO analyses and finds excellent agreement with ΛCDM cosmology, establishing void-galaxy cross-correlation as a robust cosmological probe.

ABSTRACT

We present measurements of the anisotropic cross-correlation of galaxies and cosmic voids in data from the Sloan Digital Sky Survey Main Galaxy Sample (MGS), Baryon Oscillation Spectroscopic Survey (BOSS) and extended BOSS (eBOSS) luminous red galaxy catalogues from SDSS Data Releases 7, 12 and 16, covering the redshift range $0.07<z<1.0$. As in our previous work analysing voids in subsets of these data, we use a reconstruction method applied to the galaxy data before void-finding in order to remove selection biases when constructing the void samples. We report results of a joint fit to the multipole moments of the measured cross-correlation for the growth rate of structure, $f\sigma_8(z)$, and the ratio $D_\mathrm{M}(z)/D_\mathrm{H}(z)$ of the comoving angular diameter distance to the Hubble distance, in six redshift bins. For $D_\mathrm{M}/D_\mathrm{H}$, we are able to achieve a significantly higher precision than that obtained from analyses of the baryon acoustic oscillations (BAO) and galaxy clustering in the same datasets. Our growth rate measurements are of lower precision but still comparable with galaxy clustering results. For both quantities, the results agree well with the expectations for a $\Lambda$CDM model. Assuming a flat Universe, our results correspond to a measurement of the matter density parameter $\Omega_\mathrm{m}=0.337^{+0.026}_{-0.029}$. For more general models the degeneracy directions obtained are consistent with and complementary to those from other cosmological probes. These results consolidate void-galaxy cross-correlation measurements as a pillar of modern observational cosmology.

Motivation & Objective

• To measure the growth rate of structure 𝑓𝜎8(𝑧) and the Alcock-Paczynski distance ratio 𝐷M(𝑧)/𝐷H(𝑧) using void-galaxy cross-correlations in SDSS data.
• To apply redshift-space reconstruction to mitigate selection biases in void-finding and improve measurement accuracy.
• To test the consistency of void-based cosmological constraints with the standard ΛCDM model across 0.07 < 𝑧 < 1.0.
• To demonstrate the robustness of void-galaxy cross-correlation as a complementary probe to BAO and galaxy clustering.
• To provide a unified, high-precision analysis across MGS, BOSS, and eBOSS datasets using a consistent methodology.

Proposed method

• Uses galaxy redshift data from SDSS MGS, BOSS, and eBOSS (DR7, DR12, DR16) covering 0.07 < 𝑧 < 1.0.
• Applies redshift-space reconstruction to galaxy catalogs before void-finding to reduce selection function biases.
• Employs the ZOBOV void-finder and the Revolver code to identify voids and compute void-galaxy cross-correlation functions.
• Measures multipoles of the anisotropic cross-correlation function to extract 𝑓𝜎8(𝑧) and 𝐷M(𝑧)/𝐷H(𝑧) in six redshift bins.
• Performs a joint fit to the multipoles using a likelihood framework with error estimation from mock galaxy catalogs.
• Validates results using full 𝑁-body and approximate gravity mock simulations to quantify systematic errors.

Experimental results

Research questions

• RQ1 Can void-galaxy cross-correlation measurements provide competitive constraints on 𝐷M/𝐷H and 𝑓𝜎8 compared to BAO and galaxy clustering?
• RQ2 To what extent does redshift-space reconstruction improve the accuracy of void-based cosmological measurements?
• RQ3 How do void-based constraints on 𝐷M/𝐷H and 𝑓𝜎8 compare with ΛCDM predictions across 0.07 < 𝑧 < 1.0?
• RQ4 Are systematic errors from void-finding and reconstruction negligible compared to statistical uncertainties in this analysis?
• RQ5 Can void-galaxy cross-correlation serve as a robust, independent probe of cosmic expansion and structure growth?

Key findings

• The analysis achieves a higher precision for the distance ratio 𝐷M(𝑧)/𝐷H than BAO-based measurements in the same datasets.
• The growth rate measurements 𝑓𝜎8(𝑧) are of comparable precision to those from galaxy clustering, though with lower signal-to-noise.
• The joint constraints on 𝑓𝜎8 and 𝐷M/𝐷H are in excellent agreement with the flat ΛCDM model across the redshift range 0.15 ≤ 𝑧 ≤ 0.69.
• The inferred matter density parameter is Ωm = 0.337+0.026−0.029 under the assumption of a flat Universe.
• Systematic errors from void-finding and reconstruction are found to be small compared to statistical uncertainties, confirming methodological robustness.
• The results demonstrate that void-galaxy cross-correlation is a complementary and reliable probe of cosmological parameters, especially for low-redshift geometrical tests.