When density fluctuations collapse gravitationally out of the
expanding cosmological background universe to form galaxies, the secondary
energy release which results can affect their subsequent evolution profoundly.
Martel and Shapiro
(1999;
2000
[
astro-ph];
2001)
focus on the effects of one form of such
energy release - explosions, such as might result from the supernovae which
end the lives of the first generation of massive stars to form inside
protogalaxies. They are particularly interested in the consequences of the
nonspherical geometry and continuous infall which are characteristic of
galaxy formation from realistic initial and boundary conditions.
As an idealized model which serves to illustrate and quantify the importance
of these effects, they study the effect of explosions on the quasi-spherical
objects which form at the intersections of filaments in the plane of
a cosmological pancake, as a result of gravitational instability and
fragmentation of the pancake. They study the formation and evolution of these
"galaxies," subject to the explosive injection of energy at their centers,
by numerical gas dynamical simulation in 3D utilizing our new, anisotropic
version of Smoothed Particle Hydrodynamics, Adaptive SPH ("ASPH"), with a
P3M gravity solver. Their results include the following:
They find that blow-out and blow-away are generically
anisotropic events which channel energy and mass loss outward
preferentially along the symmetry axis of the local pancake and away from the
intersections of filaments in the pancake plane.
This means that metal ejection from dwarf galaxies
at high redshift due to explosive energy release is less likely to
pollute the local filaments and pancake in which the dwarf galaxies
reside and more likely to channel the metals away from those denser regions.
Despite the complete blow-away of gas
initially in the dark matter potential well of the "galaxy"
by the large
explosion simulated here, continuous infall is not completely halted
in the directions away from the preferred direction of blow-out, so infall
partially replenishes the gas which is blown-away.