Isocurvature baryon-dominated open universe - Structure of galactic halos

Abstract

Structure of galactic halos in the isocurvature baryon-dominated open universe models is calculated. The halos' rotation curves are calculated analytically, based on the secondary infall paradigm. The nonvanishing curvature of the expanding universe introduces scale dependence of final virial structure of the halos, assuming they are formed dissipationlessly by hierarchical clustering. For primordial scale-free power spectra, with a spectral index in the range of n = 0 to -1, and Omega(0) of about 0.1, the predicted galactic halos rotation curves are found to be steeply decreasing with radius. Given the observed amplitude and extent of the rotation curves of giant spiral galaxies and the nucleosynthesis bounds on the baryon mean density, the allowed range of parameters yields only halos with falling rotation curves, in clear disagreement with the observed flat galactic rotation curves. 33 refs.