The sparkling Universe: the coherent motions of cosmic voids

Abstract

We compute the bulk motions of cosmic voids, using a $\Lambda$CDM numerical simulation considering the mean velocities of the dark matter inside the void itself and that of the haloes in the surrounding shell. We find coincident values of these two measures in the range $\sim$ 300-400 km/s, not far from the expected mean peculiar velocities of groups and galaxy clusters. When analysing the distribution of the pairwise relative velocities of voids, we find a remarkable bimodal behaviour consistent with an excess of both systematically approaching and receding voids. We determine that the origin of this bimodality resides in the void large scale environment, since once voids are classified into void-in-void (R-type) or void-in-cloud (S-type), R-types are found mutually receding away, while S-types approach each other. The magnitude of these systematic relative velocities account for more than 100 km/s, reaching large coherence lengths of up to 200 h${}^{-1}$ Mpc . We have used samples of voids from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7) and the peculiar velocity field inferred from linear theory, finding fully consistent results with the simulation predictions. Thus, their relative motion suggests a scenario of a sparkling Universe, with approaching and receding voids according to their local environment.

6 pages, 4 Figures, accepted for publication in MNRAS Letters

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• Precision cosmology with voids in the final BOSS data
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• 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
• Voids in cosmological simulations over cosmic time
• Clustering and Bias Measurements of SDSS Voids
• Testing $f(R)$ Gravity With Scale Dependent Cosmic Void Velocity Profiles
• The sparkling Universe: a scenario for cosmic void motions
• The sparkling Universe: Clustering of voids and void clumps
• Gravitational lens optical scalars in terms of energy-momentum distributions in the cosmological framework
• Voids and Superstructures: correlations and induced large-scale velocity flows
• Imprints of the cosmic void evolution on the baryon processes inside galaxy haloes
• Challenges in Constraining Gravity with Cosmic Voids
• Unveiling the Universe with Emerging Cosmological Probes
• A possible role for the merger of clusters/voids in the cosmological expansion
• The galaxy bias profile of cosmic voids