Shapes and orientations of massive halos in the statistically anisotropic universe

TL;DR

This study explores how statistical anisotropy in matter distribution influences the shapes and orientations of galaxy cluster halos, revealing significant orientation alignments that could serve as observational probes of anisotropy.

Contribution

The paper demonstrates that halo orientations are significantly affected by statistical anisotropy, especially for massive halos, while shapes remain largely unaffected, providing new insights into anisotropic universe models.

Findings

Halo orientations align with the SA direction, especially for massive halos.

Halo shapes show little dependence on statistical anisotropy.

Projected halo shapes could be used to probe SA observationally.

Abstract

We investigate how statistical anisotropy (SA) in matter distributions affects the distributions of shapes and orientations of cluster-sized halos, using cosmological $N$-body simulations that incorporate SA. While the three-dimensional halo shape parameters show little dependence on SA, we find that halo orientations are significantly influenced, with halos tending to align either perpendicular or parallel to the SA direction. This SA-induced alignment becomes more prominent for more massive halos. We also study other vector quantities associated with the dynamics of halos, such as bulk velocity and angular momentum vectors. We find that their dependences on the SA are smaller than those of the orientation vectors. Our findings suggest that observational measurements of projected halo shapes derived from galaxy cluster-galaxy lensing could provide a novel probe of SA in the universe.