Date Published:

April 1, 2016

Abstract:

Sound waves from the primordial fluctuations of the Universe imprintedin the large-scale structure, called baryon acoustic oscillations(BAOs), can be used as standard rulers to measure the scale of theUniverse. These oscillations have already been detected in thedistribution of galaxies. Here we propose to measure BAOs from thetroughs (minima) of the density field. Based on two sets of accuratemock halo catalogues with and without BAOs in the seed initialconditions, we demonstrate that the BAO signal cannot be obtained fromthe clustering of classical disjoint voids, but it is clearly detectedfrom overlapping voids. The latter represent an estimate of all troughsof the density field. We compute them from the empty circumspherecenters constrained by tetrahedra of galaxies using Delaunaytriangulation. Our theoretical models based on an unprecedented largeset of detailed simulated void catalogues are remarkably well confirmedby observational data. We use the largest recently publicly availablesample of luminous red galaxies from SDSS-III BOSS DR11 to unveil forthe first time a >3 σ BAO detection from voids in observations.Since voids are nearly isotropically expanding regions, their centersrepresent the most quiet places in the Universe, keeping in mind thecosmos origin and providing a new promising window in the analysis ofthe cosmological large-scale structure from galaxy surveys.

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