The sparkling Universe: clustering of voids and void clumps

LARES, MARCELO; RUIZ, ANDRÉS N.; LUPARELLO, HELIANA E.; CECCARELLI, LAURA; GARCIA LAMBAS, DIEGO; PAZ, DANTE J.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2017 vol. 468 p. 4822 - 4830

0035-8711

We analyse the clustering of cosmic voids using a numerical simulationand the main galaxy sample from the Sloan Digital Sky Survey. We takeinto account the classification of voids into two types that resembledifferent evolutionary modes: those with a rising integrated densityprofile (void-in-void mode or R-type) and voids with shells(void-in-cloud mode or S-type). The results show that voids of the sametype have stronger clustering than the full sample. We use thecorrelation analysis to define void clumps, associations with at leasttwo voids separated by a distance of at most the mean void separation.In order to study the spatial configuration of void clumps, we computethe minimal spanning tree and analyse their multiplicity, maximum lengthand elongation parameter. We further study the dynamics of the smallersphere that enclose all the voids in each clump. Although the globaldensities of void clumps are different according to their member-voidtypes, the bulk motions of these spheres are remarkably lower than thoseof randomly placed spheres with the same radius distribution. Inaddition, the coherence of pairwise void motions does not stronglydepend on whether voids belong to the same clump. Void clumps are usefulto analyse the large-scale flows around voids, since voids embedded inlarge underdense regions are mostly in the void-in-void regime, wherethe expansion of the larger region produces the separation of voids.Similarly, voids around overdense regions form clumps that are incollapse, as reflected in the relative velocities of voids that aremostly approaching.