How massive neutrinos reshape the cosmic web

TL;DR

This paper investigates how massive neutrinos influence the cosmic web's structure using simulations, revealing their impact on density distributions, web classification, and the potential of MST analysis for large-scale structure studies.

Contribution

It introduces the use of minimum spanning tree analysis on simulated cosmic web data to distinguish effects of massive neutrinos from baryonic physics, highlighting its potential for observational applications.

Findings

Massive neutrinos decrease the volume of clusters and voids.

Neutrino mass shifts the density distribution towards higher densities.

Most MST edges are in filaments, sensitive to neutrino mass.

Abstract

We explore the effects of massive neutrinos on the cosmic web using the FLAMINGO simulations. We classify the cosmic web into voids, sheets, filaments, and clusters, and find that massive neutrinos affect the environment by decreasing the volume occupied by clusters and voids. We find that increasing the neutrino mass shifts the volume-weighted density distribution towards higher densities and leads to a more narrow density distribution, which we interpret as neutrinos delaying structure formation. We construct the minimum spanning tree (MST) graph from the subhaloes, adopting a number density chosen to match that expected for DESI-like observations. We show that most MST edges lie in filaments, approximately 70% throughout different simulations, which we link to its sensitivity to neutrino mass. We also link the MST's edge length signal at different scales to different cosmic web environments, with clusters dominating the signal at small scales, voids at longer scales, and filaments at intermediate scales. The strong correlation between MST edges and cosmic web environments reinforces the MST's potential to be used as a classifier for large-scale structure in galaxy surveys. We compare the effects of baryonic physics and massive neutrinos and find that each produces distinct signatures in MST edge lengths. This analysis is performed in 3D space, using the true positions of subhaloes and not accounting for redshift space distortions. Nevertheless, these results emphasise the MST's capability to go beyond two-point statistics, motivating future applications to real observational data.