The sparkling Universe: a scenario for cosmic void motions

Abstract

We perform a statistical study of the global motion of cosmic voids using both a numerical simulation and observational data. We analyse their relation to large-scale mass flows and the physical effects that drive those motions. We analyse the bulk motions of voids, defined by the mean velocity of haloes in the surrounding shells in the numerical simulation, and by galaxies in the Sloan Digital Sky Survey Data Release 7. We find void mean bulk velocities close to 400 km/s, comparable to those of haloes (~ 500-600 km/s), depending on void size and the large-scale environment. Statistically, small voids move faster than large ones, and voids in relatively higher density environments have higher bulk velocities than those placed in large underdense regions. Also, we analyze the mean mass density around voids finding, as expected, large-scale overdensities (underdensities) along (opposite to) the void motion direction, suggesting that void motions respond to a pull-push mechanism. This contrasts with massive cluster motions who are mainly governed by the pull of the large-scale overdense regions. Our analysis of void pairwise velocities shows how their relative motions are generated by large-scale density fluctuations. In agreement with linear theory, voids embedded in low (high) density regions mutually recede (attract) each other, providing the general mechanism to understand the bimodal behavior of void motions. In order to compare the theoretical results and the observations we have inferred void motions in the SDSS using linear theory, finding that the estimated observational void motions are in statisticalagreement with the results of the simulation. Regarding large-scale flows, our results suggest a scenario of galaxies and galaxy systems flowing away from void centers with the additional, and morerelevant, contribution of the void bulk motion to the total velocity.

10 pages, 10 figures, Accepted for publication in MNRAS

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Cited by in corpus (13)

• Cosmic Voids and Void Lensing in the Dark Energy Survey Science Verification Data
• Precision cosmology with voids in the final BOSS data
• Redshift-space effects in voids and their impact on cosmological tests. Part I: the void size function
• Constraints on the growth of structure around cosmic voids in eBOSS DR14
• Redshift-space effects in voids and their impact on cosmological tests. Part II: the void-galaxy cross-correlation function
• Testing the spherical evolution of cosmic voids
• Guess the cheese flavour by the size of its holes: A cosmological test using the abundance of Popcorn voids
• The sparkling Universe: Clustering of voids and void clumps
• Voids and Superstructures: correlations and induced large-scale velocity flows
• Surveying the Local Supercluster Plane
• Unveiling the Universe with Emerging Cosmological Probes
• DarkAI: Reconstructing the density, velocity and tidal field of dark matter from a DESI-like bright galaxy sample
• The galaxy bias profile of cosmic voids