Properties of Cosmological Filaments extracted from Eulerian Simulations

TL;DR

This study introduces a new parallel algorithm to analyze large cosmological simulations, revealing detailed properties of filaments, their scaling relations, and the effects of various gas physics processes on their thermal and dynamic states.

Contribution

The paper presents a novel parallel algorithm within the VisIt framework for large-scale filament analysis in cosmological simulations, enabling extensive catalogues and detailed property investigations.

Findings

Longest filaments reach about 200 Mpc in length.

Radiative cooling lowers filament temperatures significantly.

AGN feedback can heat filament gas, affecting thermal properties.

Abstract

Using a new parallel algorithm implemented within the VisIt framework, we analysed large cosmological grid simulations to study the properties of baryons in filaments. The procedure allows us to build large catalogues with up to $\sim 3 \cdot 10^4$ filaments per simulated volume and to investigate the properties of cosmic filaments for very large volumes at high resolution (up to $300^3 ~\rm Mpc^3$ simulated with $2048^3$ cells). We determined scaling relations for the mass, volume, length and temperature of filaments and compared them to those of galaxy clusters. The longest filaments have a total length of about $200 ~\rm Mpc$ with a mass of several $10^{15} M_{\odot}$. We also investigated the effects of different gas physics. Radiative cooling significantly modifies the thermal properties of the warm-hot-intergalactic medium of filaments, mainly by lowering their mean temperature via line cooling. On the other hand, powerful feedback from active galactic nuclei in surrounding halos can heat up the gas in filaments. The impact of shock-accelerated cosmic rays from diffusive shock acceleration on filaments is small and the ratio of between cosmic ray and gas pressure within filaments is of the order of $\sim 10-20$ percent.