VORTICAL MOTIONS OF BARYONIC GAS IN THE COSMIC WEB: GROWTH HISTORY AND SCALING RELATION

The vortical motions of the baryonic gas residing in large-scale structures are investigated by cosmological hydrodynamic simulations. Proceeding in the formation of the cosmic web, the vortical motions of baryonic matter are pumped up by baroclinity in two stages, i.e., the formation of sheets and filaments. The mean curl velocities are about <1, 1-10, 10-150, and 5-50 km s(-1) in voids, sheets, filaments, and knots at z = 0, respectively. The scaling of the vortical velocity of gas can be well described by the She-Leveque hierarchical turbulence model in the range of l < 0.65(1.50) h(-1) Mpc in a simulation with a box of size 25(100) h(-1) Mpc. The fractal Hausdorff dimension of vortical motions, d, revealed by velocity structure functions, is similar to 2.1-2.3(similar to 1.8-2.1). It is slightly larger than the fractal dimension of mass distribution in filaments, D-f similar to 1.9-2.2, and smaller than the fractal dimension of sheets, D-s similar to 2.4-2.7. The vortical kinetic energy of baryonic gas is mainly transported by filaments. Both scalings of mass distribution and vortical velocity increments show distinctive transitions at the turning scale of similar to 0.65(1.50) h(-1) Mpc, which may be closely related to the characteristic radius of density filaments.