Relative distribution of dark matter, gas, and stars around cosmic filaments in the IllustrisTNG simulation

Abstract

We present a comprehensive study of the distribution of matter around different populations of large-scale cosmic filaments, using the IllustrisTNG simulation at z=0. We computed the dark matter (DM), gas, and stellar radial density profiles of filaments, and we characterise the distribution of the baryon fraction in these structures. We find that baryons exactly follow the underlying DM distribution only down to r~7 Mpc to the filament spines. At shorter distances (r<7 Mpc), the baryon fraction profile of filaments departs from the cosmic value $\Omega_\mathrm{b} / \Omega_\mathrm{m}$. While in the r~0.7-7 Mpc radial domain this departure is due to the radial accretion of the warm-hot intergalactic medium (WHIM) towards the filament cores (creating an excess of baryons with respect to the cosmic fraction), the cores of filaments (r<0.7 Mpc) show a clear baryon depletion instead. The analysis of the efficiency of active galactic nuclei (AGN) feedback events in filaments reveals that they are potentially powerful enough to eject gas outside of the gravitational potential wells of filaments. We show that the large-scale environment (i.e. denser versus less dense, hotter versus colder regions) has a non-negligible effect on the absolute values of the DM, gas, and stellar densities around filaments. Nevertheless, the relative distribution of baryons with respect to the underlying DM density field is found to be independent of the filament population. Finally, we provide scaling relations between the gas density, temperature, and pressure for the different populations of cosmic filaments. We compare these relations to those pertaining to clusters of galaxies, and find that these cosmic structures occupy separate regions of the density-temperature and density-pressure planes.