We investigate the influence of nonequilibrium thermodynamics on cosmological structure formation. In this paper, we consider the collapse of the planar perturbations usually called "Zeldovich pancakes." We have developed for that purpose a new two-fluid (gas and dark matter) hydrodynamical code, with three different thermodynamical species: electrons, ions, and neutral particles, Te ≠ Ti ≠ Tn. We describe in detail the complex structure of accretion shock waves. We include several relevant processes for a low-density, high-temperature collisional plasma: nonequilibrium chemical reactions, cooling, shock heating, thermal energy equipartition between electrons, ions, and neutral particles, and electronic conduction. We find two different regions in the pancake structure: a thermal precursor ahead of the compression front and an equipartition wave after the compression front, where electron and ion temperatures differ significantly. This complex structure may have two interesting consequences: preheating of unshocked regions in the vicinity of massive X-ray clusters and ion and electron temperature differences in the outer regions of X-ray clusters.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
- Cosmology: theory
- Methods: numerical