Cosmic gas highways in C-EAGLE simulations

Abstract

A substantial fraction of the cosmic baryons is expected to hide in the form of diffuse warm-hot intergalactic medium (WHIM), the majority of which resides in the filaments of the Cosmic Web and has proven very difficult to detect due to its low density. Close to galaxy clusters, the filament gas is affected by the cluster's gravitational potential and attains substantial infall velocities, eventually undergoing a termination shock which may boost its X-ray signal. We aim to identify the optimal locations of the enhanced X-ray emission and absorption arising from cluster-filament interactions, as well as improve our understanding of the various physical processes affecting the WHIM as it approaches the cluster. We applied the DisPerSE filament finder to the galaxy distribution in the surroundings of a Coma-like ($M_{200}\sim 10^{15.4}{\mathrm{M}}_{\odot }$) simulated C-EAGLE galaxy cluster. We characterised the thermodynamic properties of the gas in such filaments as well as their dependence on distance from the cluster, and provided a physical interpretation for the results. The identified filaments account for $\sim 50$% of the hot WHIM ($T>10^{5.5}$ K) in the cluster vicinity. The filament gas is in approximate free-fall all the way down to $\sim 2r_{200}$ from the cluster, at which stage it begins to slow down due to the increasing pressure of the ambient gas. The deceleration is accompanied by the conversion of gas bulk kinetic energy into heat and the increase of density and temperature from the general Cosmic Web level of $\rho \sim 10{\rho }_{\mathrm{av}}$ and $T=10^5-10^6$ K towards $\rho \sim 100{\rho }_{\mathrm{av}}$ and $T=10^7-10^8$ K near the cluster boundary. We conclude that the detection of the cosmic filaments of galaxies around clusters may provide a practical observational avenue for locating the densest and hottest phase of the missing baryons.

20 pages, 16 figures, accepted for publication in A&A

References in corpus (11)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations
• Detection of hot gas in the filament connecting the clusters of galaxies Abell 222 and Abell 223
• Cosmological Shock Waves in the Large Scale Structure of the Universe: Non-gravitational Effects
• The redshift evolution of massive galaxy clusters in the MACSIS simulations
• The Abell 3391/95 galaxy cluster system: A 15 Mpc intergalactic medium emission filament, a warm gas bridge, infalling matter clumps, and (re-) accelerated plasma discovered by combining SRG/eROSITA data with ASKAP/EMU and DECam data
• First detection of stacked X-ray emission from cosmic web filaments
• An EAGLE view of the missing baryons
• Mapping and characterisation of cosmic filaments in galaxy cluster outskirts: strategies and forecasts for observations from simulations
• The ThreeHundred: the structure and properties of cosmic filaments in the outskirts of galaxy clusters
• The Three Hundred Project: The gas disruption of infalling objects in cluster environments