1510.00712
The sparkling universe: the coherent motions of cosmic voids
Lambas, et al
Compute the bulk motions of cosmic voids, using LCDM numerical simulation considering the mean velocities of the DM inside the void itself and that of the haloes in the surrounding shell. Find coincident values of these two measures in the range ~300-400 km/s, not far from the expected mean peculiar velocities of groups and galaxy clusters. When analyzing the distribution of the pairwise relative velocities of voids, find a remarkable bimodal behavior consistent with an excess of both systematically approaching and receding voids. 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: voids with continuously rising integrated density profiles) or void-in-cloud (S-type: void samples that exhibit overdense shell), 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 Mpc/h. Use samples of voids from 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.
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