Cosmic homogeneity: a spectroscopic and model-independent measurement

TL;DR

This paper presents the first spectroscopic, model-independent measurement of the angular homogeneity scale using galaxy data, confirming the Universe's large-scale homogeneity and its evolution over time.

Contribution

It introduces a novel spectroscopic and model-independent method to measure the angular homogeneity scale, supporting the standard cosmological model.

Findings

Galaxy distribution is homogeneous at large scales within 0.46 < z < 0.62.

The homogeneity scale $ heta_{ m h}$ increases with redshift.

Results align with the standard cosmological paradigm.

Abstract

Cosmology relies on the Cosmological Principle, i.e., the hypothesis that the Universe is homogeneous and isotropic on large scales. This implies in particular that the counts of galaxies should approach a homogeneous scaling with volume at sufficiently large scales. Testing homogeneity is crucial to obtain a correct interpretation of the physical assumptions underlying the current cosmic acceleration and structure formation of the Universe. In this Letter, we use the Baryon Oscillation Spectroscopic Survey to make the first spectroscopic and model-independent measurements of the angular homogeneity scale $\theta_{\rm h}$. Applying four statistical estimators, we show that the angular distribution of galaxies in the range 0.46 < z < 0.62 is consistent with homogeneity at large scales, and that $\theta_{\rm h}$ varies with redshift, indicating a smoother Universe in the past. These results are in agreement with the foundations of the standard cosmological paradigm.