http://arxiv.org/abs/2201.12665
By decomposing velocity dispersions into nonspin- and spin-induced, mean flow and dispersions are analytically solved for axisymmetric rotating and growing halos. The polar flow can be neglected and azimuthal flow is directly related to dispersions. The fictitious (“Reynolds”) stress acts on radial flow to enable energy transfer from mean flow to random motion and maximize system entropy. For large halos (high peak height $\nu$ at early stage of halo life) with constant concentration, there exists a self-similar radial flow (outward in core and inward in outer region). Halo mass, size and specific angular momentum increase linearly with time via fast mass accretion. Halo core spins faster than outer region. Large halos rotate with an angular velocity proportional to Hubble parameter and spin-induced dispersion is dominant. All specific energies (radial/rotational/kinetic/potential) are time-invariant. Both halo spin (~0.031) and anisotropic parameters can be analytically derived. For “small” halos with stable core and slow mass accretion (low peak height $\nu$ at late stage of halo life), radial flow vanishes. Small halos rotate with constant angular velocity and non-spin dispersion is dominant. Small halos are more spherical in shape, incompressible, and isotropic. Radial and azimuthal dispersions are comparable and greater than polar dispersion. Due to finite spin, kinetic energy is not equipartitioned with the greatest energy along azimuthal direction. Halos are hotter with faster spin. Halo relaxation (evolution) from early to late stage involves continuous variation of shape, density, mean flow, momentum, and energy. During relaxation, halo isotopically “stretches” with conserved specific angular kinetic energy, increasing halo concentration and momentum of inertial. Therefore, halo “stretching” leads to decreasing angular velocity and increasing angular momentum and spin parameter.
Z. Xu
Tue, 1 Feb 22
19/73
Comments: 14 Figure and 4 Tables