Effect of Massive Neutrinos on the Position of Cold Dark Matter Halo: Revealed via Delaunay Triangulation Void

TL;DR

This study uses cosmological simulations to show how massive neutrinos influence the spatial distribution of dark matter halos, affecting void sizes and halo clustering, which can be observed in galaxy surveys.

Contribution

It reveals the local impact of massive neutrinos on CDM halo distribution through Delaunay Triangulation void analysis, a novel approach in this context.

Findings

Smaller voids are in regions with higher neutrino abundance.

Larger voids are in regions with lower neutrino abundance.

Neutrino effects suppress halo two-point correlation on ~1 Mpc/h scales.

Abstract

Using cosmological $N$-body simulation which coevolves cold dark matter (CDM) and neutrino particles, we discover the local effect of massive neutrinos on the spatial distribution of CDM halos, reflected on properties of the Delaunay Triangulation (DT) voids. Smaller voids are generally in regions with higher neutrino abundance and so their surrounding halos are impacted by a stronger neutrino free streaming. This makes the voids larger (surrounding halos being washed outward the void center). On the contrary, larger voids are generally in regions with lower neutrino abundance and so their surrounding halos are less impacted by neutrino free streaming, making the voids smaller (surrounding halos being squeezed toward the void center). This characteristic change of the spatial distribution of the halos suppresses the 2-point correlation function of halos on scales $\sim$ 1 Mpc$/h$ and significantly skews the number function of the DT voids, which serve as measurable neutrino effects in current or future galaxy surveys.