Bending the web: exploring the impact of modified gravity on the density field and halo properties within the cosmic web

TL;DR

This paper explores how modified gravity models influence the large-scale structure and halo properties within the cosmic web, revealing distinctive density and angular momentum features that can help differentiate these models from standard cosmology.

Contribution

It provides a detailed analysis of the impact of f(R) and nDGP modified gravity models on the cosmic web's density and halo properties using N-body simulations, highlighting environment-dependent effects.

Findings

Dark matter density PDF shifts towards lower densities in stronger MG variants.

Halo angular momentum increases by up to 15% in f(R) models compared to LCDM.

Environmental segregation reveals complex trends in halo mass function and clustering statistics.

Abstract

This work investigates the impact of different Modified Gravity (MG) models on the large-scale structures (LSS) properties in relation to the cosmic web (CW), using N-body simulations of f(R) and nDGP models. We analyse the impact of the MG effect on the density field through density distribution and clustering statistics, and assess its influence on halo properties by examining the halo mass function and spin. We find that the PDF of dark matter density fields shift towards lower densities for stronger variants of f(R) and nDGP. Additionally, when segregated into CW environments, the stronger variants show a higher mean density in knots, and a lower mean density in voids compared to LCDM. For higher-order clustering statistics relative to LCDM, the scale-dependent f(R) variants exhibit a greater non-monotonic deviation as a function of scale when segregated into environments, compared to nDGP. Additionally, the halo mass function separated into CW environments shows a similar behaviour, introducing complex trends as a function of mass for f(R) and nDGP models. We also report up to a 15% enhancement in the angular momentum of halos in f(R) gravity models compared to LCDM, with similar differences when considering environmental segregation. We demonstrate that this difference in the spin arises largely due to different tidal torquing across the various MG models. Therefore, studying higher-order statistics of the cosmological fields and halo properties separated into CW components probes the additional physics contained within the MG models. We conclude that considering the effect of CW in MG studies increases the constraining power of these LSS statistics, and can further aid the distinction between the cosmologies that have an identical expansion history to the standard LCDM but differing underlying physics, such as the MG models presented in this work.