2022/01/29 by Zhijie Xu, Xu, Zhijie
Physics and Astronomy · #Astronomy and Astrophysical Research #Stellar, planetary, and galactic studies #Galaxies: Formation, Evolution, Phenomena
paper · pdf · doi:10.48550/arxiv.2201.12665
By decomposing velocity dispersion into non-spin and spin-induced, mean flow\nand dispersion are analytically solved for axisymmetric rotating and growing\nhalos. The polar flow can be neglected and azimuthal flow is directly related\nto dispersion. The fictitious ("Reynolds") stress acts on mean flow to enable\nenergy transfer from mean flow to random motion and maximize system entropy.\nFor large halos (high peak height \ν at early stage of halo life) with\nconstant concentration, there exists a self-similar radial flow (outward in\ncore and inward in outer region). Halo mass, size and specific angular momentum\nincrease linearly with time via fast mass accretion. Halo core spins faster\nthan outer region. Large halos rotate with an angular velocity proportional to\nHubble parameter and spin-induced dispersion is dominant. All specific energies\n(radial/rotational/kinetic/potential) are time-invariant. Both halo spin\n(\∼0.031) and anisotropic parameters can be analytically derived. For\n"small" halos with stable core and slow mass accretion (low peak height \ν\nat late stage of halo life), radial flow vanishes. Small halos rotate with\nconstant angular velocity and non-spin axial dispersion is dominant. Small\nhalos are spherical in shape, incompressible, and isotropic. Radial and\nazimuthal dispersion are comparable and greater than polar dispersion. Due to\nfinite spin, kinetic energy is not equipartitioned with the greatest energy\nalong azimuthal direction. Different from normal matter, small halos are hotter\nwith faster spin. Halo relaxation from early to late stage involves variation\nof shape, density, mean flow, momentum, and energy. During relaxation, halo\nisotopically "stretches" with conserved specific rotational kinetic energy,\nincreasing concentration and momentum of inertial. Halo "stretching" leads to\ndecreasing angular velocity, increasing angular momentum and spin parameter.\n