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

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