  As an idealized model of the effects of energy release by supernovae during
galaxy formation, we consider an explosion at the center of a halo which forms
at the intersection of filaments in the plane of a cosmological pancake by
gravitational instability during pancake collapse. Such halos resemble the
virialized objects found in N-body simulations in a CDM universe and,
therefore, serve as a convenient, scale-free test-bed model for galaxy
formation. ASPH/P3M simulations reveal that such explosions are anisotropic.
The energy and metals are channeled into the low density regions, away from the
pancake plane. The pancake remains essentially undisturbed, even if the
explosion is strong enough to blow away all the gas located inside the halo at
the onset of the explosion and reheat the IGM surrounding the pancake. Infall
quickly replenishes this ejected gas and gradually restores the gas fraction as
the halo mass continues to grow. Estimates of the collapse epoch and SN
energy-release for galaxies of different mass in the CDM model can relate these
results to scale-dependent questions of blow-out and blow-away and their
implication for early IGM heating and metal enrichment and the creation of
dark-matter-dominated dwarf galaxies.
