Signatures of the Primordial Universe from Its Emptiness: Measurement of Baryon Acoustic Oscillations from Minima of the Density Field

TL;DR

This paper demonstrates that baryon acoustic oscillations can be detected from overlapping voids in the large-scale structure of the universe, providing a new method to measure cosmic scales with high significance.

Contribution

It introduces a novel approach to measure BAOs from the minima of the density field using overlapping voids, confirmed by simulations and observational data.

Findings

BAO signals are detectable from overlapping voids but not from disjoint ones.

The method achieves a >3σ BAO detection in SDSS-III BOSS data.

Voids serve as quiet, nearly isotropic regions ideal for cosmological measurements.

Abstract

Sound waves from the primordial fluctuations of the Universe imprinted in the large-scale structure, called baryon acoustic oscillations (BAOs), can be used as standard rulers to measure the scale of the Universe. These oscillations have already been detected in the distribution of galaxies. Here we propose to measure BAOs from the troughs (minima) of the density field. Based on two sets of accurate mock halo catalogues with and without BAOs in the seed initial conditions, we demonstrate that the BAO signal cannot be obtained from the clustering of classical disjoint voids, but is clearly detected from overlapping voids. The latter represent an estimate of all troughs of the density field. We compute them from the empty circumsphere centers constrained by tetrahedra of galaxies using Delaunay triangulation. Our theoretical models based on an unprecedented large set of detailed simulated void catalogues are remarkably well confirmed by observational data. We use the largest recently publicly available sample of luminous red galaxies from SDSS-III BOSS DR11 to unveil for the first time a >3$\sigma$ BAO detection from voids in observations. Since voids are nearly isotropically expanding regions, their centers represent the most quiet places in the Universe, keeping in mind the cosmos origin and providing a new promising window in the analysis of the cosmological large-scale structure from galaxy surveys.