Open AccessSelf‐similar collapse of collisional gas in an expanding universe
Author(s) -
Chuzhoy Leonid,
Nusser Adi
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03865.x
Subject(s) - physics , adiabatic process , perturbation (astronomy) , hydrostatic equilibrium , astrophysics , classical mechanics , galaxy cluster , galaxy , quantum mechanics
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 centre of a spherical perturbation with and the gas is in quasi‐hydrostatic equilibrium (pressure‐supported) and has an asymptotic power‐law density profile, independent of γ . For the profile depends on γ , the pressure is finite, the temperature decreases inwards, and gravity dominates pressure, causing a continuous inward flow. Although for the temperature decreases at the centre, 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 centre 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 centre. The solutions and the asymptotic behaviour are relevant for modelling the gas distribution in galaxy clusters and pancake‐like superclusters, and for determining the structure of haloes of self‐interacting dark matter with large interaction cross‐section.