Alignments of Voids in the Cosmic Web

TL;DR

This paper studies the shapes and alignments of cosmic voids in large-scale structure, revealing their strong correlation with the tidal field and the influence of long-range forces on the cosmic web's organization.

Contribution

It introduces a novel void finder technique and demonstrates the significant alignment of voids with the cosmic tidal field across large scales.

Findings

Void shapes are nonspherical and slightly prolate.

Void orientations are strongly aligned over >30 Mpc/h.

Void alignments are linked to the large-scale tidal field.

Abstract

We investigate the shapes and mutual alignment of voids in the large scale matter distribution of a LCDM cosmology simulation. The voids are identified using the novel WVF void finder technique. The identified voids are quite nonspherical and slightly prolate, with axis ratios in the order of c:b:a approx. 0.5:0.7:1. Their orientations are strongly correlated with significant alignments spanning scales >30 Mpc/h. We also find an intimate link between the cosmic tidal field and the void orientations. Over a very wide range of scales we find a coherent and strong alignment of the voids with the tidal field computed from the smoothed density distribution. This orientation-tide alignment remains significant on scales exceeding twice the typical void size, which shows that the long range external field is responsible for the alignment of the voids. This confirms the view that the large scale tidal force field is the main agent for the large scale spatial organization of the Cosmic Web.