(3b) ASPH Simulations of Cosmological Gas Dynamics in 2D
Shapiro and Martel simulated the formation of large-scale structure and the
evolution of the IGM in cosmology models like CDM, with high resolution 2D
ASPH simulations (256 x 256 gas particles, 1024 x 1024
dark + gas particles, 2048 x 2048
PM grid cells).
X-ray cluster formation in the CDM model was
simulated (
Martel et al 1995; Valinia Ph.D. thesis). With Valinia,
the standard mass determination by X-ray surface brightness profile fitting
and the assumption of isothermal spheres in hydrostatic equilibrium was
tested (Valinia Ph.D. thesis).
We found that clusters
are not relaxed, virialized and hydrostatic, but are, instead, comprised of
merging subclusters. Mergers and projection effects were found to cause the
gas fraction to be overestimated and the total mass to be underestimated,
thereby contributing to the appearance of the so-called "baryon catastrophe."
The feedback of the reheating which accompanied the reionization
of the IGM on the rate of collapse of baryons out of the IGM was simulated
and the results compared with the total collapsed baryonic fraction at z = 3 in
quasar absorption lines (
Shapiro 1995;
Shapiro and Martel 1995),
showing that the ability of the
CDM model to reproduce the abundance and baryonic content of Damped Lyman Alpha
absorbers is sensitive to the feedback effect of energy release by the
collapsed fraction on the rate of growth of that collapsed fraction.