出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We discuss the nucleosynthesis and stochastic evolution of proto-galactic clouds in a model which
is motivated by cold dark matter simulations of hierarchical galaxy formation. We utilize SNinduced
star-formation within a model that follows the evolution of chemical enrichment and
energy input to the clouds by Type II and Type Ia supernovae. We include metallicity-dependent
yields for all elements at all times, and include effects of finite stellar lifetimes. We derive the
metallicity distribution functions for stars in the clouds, their age-metallicity relation, and relative
elemental abundances for a number of alpha- and Fe-group elements. More massive clouds are
only stable when one assumes an initial mass function that is not biased towards massive stars.
The observed dispersion in [a/Fe] at low [Fe/H] tends to be too large unless yields from the most
massive stars (M 35−40 M ) are suppressed. We also require mixing of protogalactic clouds
to reduce the dispersion to the observed values. We estimate that 50% of the proto-galactic
clouds were well mixed during the early star formation epoch. We also show that the observed
large dispersion in some (e.g. neutron-capture) elements can be attributed to the fact that the rare
events which produce these are prevented from adequate mixing.
