Effects of Baryonic Feedback on the Cosmic Web

TL;DR

This study investigates how baryonic feedback influences the structure and mass distribution of the cosmic web, revealing significant effects on density fields and emphasizing the need to include baryons in cosmological models.

Contribution

It introduces a modified NEXUS algorithm applied to IllustrisTNG simulations to quantify baryonic effects on cosmic web structures and their statistical properties.

Findings

Halos lose over 10% of their mass due to baryons.

Baryonic feedback causes nearly 100% suppression in the emptiest regions of the density PDF.

Most power spectrum suppression can be explained by halos with M≥10^{12} M_sun/h.

Abstract

We study the effect of baryons on the cosmic web -- halos, filaments, walls, and voids. To do so, we apply a modified version of NEXUS, a cosmic web morphological analysis algorithm, to the IllustrisTNG simulations. We find that halos lose more than $10\%$ of their mass due to baryons, mostly to filaments and a small portion to walls and voids. However, the mass transfer does not significantly shift the boundaries of structures, leaving the volume fractions of the cosmic structures largely unaffected. We quantify the effects of baryonic feedback on the power spectrum and the probability density function (PDF) of the density field for individual cosmic structures. For the power spectrum, most suppression due to feedback can be accounted for by including $M\ge10^{12}~M_\odot/h$ halos, without considering other cosmic structures. However, when examining the PDF of the density field, we find nearly $100\%$ suppression of the emptiest regions and $10\%$-level effects (boost or suppression) in the remaining regions of filaments, walls, and voids. Our results indicate the importance of modeling the effects of baryons in the whole cosmic web, not just halos, for cosmological analysis beyond two-point statistics or field-based inferences.