The impact of massive neutrinos on halo assembly bias

TL;DR

This study investigates how massive neutrinos influence halo assembly bias and related properties using large N-body simulations, finding neutrinos affect halo properties and environment but not the bias-mass relations at fixed halo mass.

Contribution

First measurement of halo assembly bias in simulations with massive neutrinos, analyzing its dependence on halo properties and environment.

Findings

Neutrinos do not affect bias-property relations at fixed mass.

Neutrinos impact halo properties and environment similarly to assembly bias.

Changes in spin and shape due to neutrinos are linked to $\sigma_8$, unlike concentration.

Abstract

Using the publicly available Quijote simulations, we present the first measurements of the assembly bias of dark matter halos in N-body simulations which include massive neutrinos. We focus on the dependence of the linear bias $b_1$ on three halo properties: 1) concentration $c$, 2) spin $\lambda$, and 3) ellipticity $s$. Although these simulations cover a large volume, superior to any future surveys, we do not detect any effect of neutrinos on the relations $b_1(c)$, $b_1(\lambda)$ and $b_1(s)$ at fixed halo mass. We further study the dependence of halo properties and environment on neutrinos, finding these quantities to be impacted by neutrino masses at the same level as assembly bias. We find that the effect of neutrinos on spin and shape can be largely attributed to the change in the cold dark matter $\sigma_8$ in neutrinos simulations, which is not the case for concentration.