Self-similar collapse of collisional gas in an expanding Universe
May, 2000Citations per year
Abstract: (arXiv)
Similarity solutions are found for the adiabatic collapse of density perturbations in a flat universe containing collisional gas only. The solutions are obtained for planar, cylindrical, and spherical perturbations with zero initial pressure. For adiabatic index , a shock develops at a fixed fraction of the current turnaround distance. Near the center of a spherical perturbations with and , the gas is in quasi-hydrostatic equilibrium (pressure supported) and has an asymptotic power law density profile, , independent of . For , the profile depends on , the pressure is finite, the temperature decreases inward, and gravity dominates pressure causing a continuous inward flow. Although for the temperature decreases at the center, the gas is pressure supported. The pressure is finite in cylindrical perturbations for , and in planar perturbations for any . We also derive the asymptotic behaviour of the gas variables near the center in a universe dominated by collisionless matter. In such a universe, the gas in a spherical perturbation with cannot be pressure supported and the temperature approaches a constant near the center. The solutions and the asymptotic behaviour are relevant for modelling the gas distribution in galaxy clusters and pancake-like superclusters, and determining the structure of haloes of self-interacting dark matter with large interaction cross section.- COSMOLOGY THEORY
- GRAVITATION
- DARK MATTER
- BARYONS
- IGM
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