Wednesday, October 31, 2012 - 4:15pm
"Turbulence driven by structure formation in the circum-galactic medium"
Abstract. The injection of turbulence in the circum-galactic medium at redshift $z = 2$ is investigated using the mesh-based hydrodynamic code enzo and a subgrid-scale (SGS) model for unresolved turbulence. Radiative cooling and heating by a uniform UV background are included in the runs, and compared with the effect of turbulence modelling. Mechanisms of gas exchange between galaxies and the surrounding medium, as well as metal enrichment, are neglected, and turbulence is here driven solely by structure formation (mergers and shocks). It has been found that turbulence, both at resolved and SGS scales, impacts mostly the warm-hot intergalactic medium (WHIM), with temperature between 10^5 and 10^7 K, mainly located around collapsed and shock heated structures, and in filaments. Typical values of the ratio of turbulent to thermal pressure is 0.1 in the WHIM, corresponding to a volume-weighted average of the SGS turbulent to thermal Doppler broadening b_t / b_therm = 0.26. In the diffuse intergalactic medium (IGM), defined in a range of baryon overdensity delta between 1 and 50, the importance of turbulence is smaller, but grows as a function of gas density.