The causal effect of environment on halo mass and concentration

Corentin Cadiou,Luisa Lucie-Smith,Hiranya V Peiris,Andrew Pontzen

doi:10.1093/mnras/stab2650

Abstract

ABSTRACT Understanding the impact of environment on the formation and evolution of dark matter haloes and galaxies is a crucial open problem. Studying statistical correlations in large simulated populations sheds some light on these impacts, but the causal effect of an environment on individual objects is harder to pinpoint. Addressing this, we present a new method for resimulating a single dark matter halo in multiple large-scale environments. In the initial conditions, we ‘splice’ (i.e. insert) the Lagrangian region of a halo into different Gaussian random fields, while enforcing consistency with the statistical properties of Lambda cold dark matter. Applying this technique, we demonstrate that the mass of haloes is primarily determined by the density structure inside their Lagrangian patches, while the haloes’ concentration is more strongly affected by environment. The splicing approach will also allow us to study, for example, the impact of the cosmic web on accretion processes and galaxy quenching.

Highlights

The growth of dark matter halos and galaxies can be most accurately computed using numerical simulations
Attaining a physical understanding of these effects of cosmological environment on individual galaxies is complicated by the wide variety of possible configurations that are generated by the Gaussian random initial conditions (ICs)
We extend the ‘genetic modification’ (GM) technique (Roth et al 2016), which is designed to construct controlled experiments in cosmological galaxy and halo formation

Summary

Introduction

The growth of dark matter halos and galaxies can be most accurately computed using numerical simulations. Attaining a physical understanding of these effects of cosmological environment on individual galaxies is complicated by the wide variety of possible configurations that are generated by the Gaussian random initial conditions (ICs). The main approach to disentangling the impact of environmental factors on galaxy formation is statistical in nature (Aubert et al 2004; Danovich et al 2012; Codis et al 2012; Kraljic et al 2019; Martizzi et al 2020). We extend the ‘genetic modification’ (GM) technique (Roth et al 2016), which is designed to construct controlled experiments in cosmological galaxy and halo formation. Our extension aims to manipulate instead the large-scale environment, while leaving the density structure of a target object’s Lagrangian patch untouched

Methods

Results

Conclusion