2025/03/09 by Wang, Yun, Li, Minxing, He, Ping
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2503.06593
Both simulations and observations indicate that the so-called missing baryons reside in the intergalactic medium (IGM) known as the warm-hot intergalactic medium (WHIM). In this paper, we employ the IllustrisTNG50-1 simulation to demonstrate that turbulence in the cosmic baryonic fluid is crucial for correctly understanding both the spatial distribution and the physical origins of the missing baryons in the universe. First, we find that dynamical effects cause the gas to be detained in low-density and intermediate-density regions, resulting in high baryon fractions, while prevent the convergence of the gas in high-density regions, leading to low baryon fractions. Second, turbulent energy is converted into thermal energy, and the injection and dissipation of turbulent energy have essentially reached a balance from z=1 to 0. This indicates that the cosmic fluid is in a steady state within this redshift range. Due to turbulent heating, as redshift decreases, an increasing amount of warm gas is heated and transitions into the WHIM, and some even into hot gas. We find that, compared with turbulence in the cosmic fluid, shocks are unimportant in intermediate-density regions and even negligible in high-density regions, both dynamically and thermodynamically. This finding not only provides the origin of WHIM in terms of both dynamics and thermodynamics, but also questions the traditional view of the shock heating and highlights the importance of turbulence in shaping the large-scale structure of the universe, particularly in the evolution of galaxies and galaxy clusters. In addition to TNG50-1, we validated our key findings with TNG50-2, TNG100-1, WIGEON, and EAGLE simulations, demonstrating that resolution, box size, and subgrid-physics variations do not affect our main conclusions.