(1) Chemistry in the Early Universe: The Role of
H_2 Molecules in Galaxy and Primordial Star Formation
Galaxies and the first stars in the universe formed billions of years ago
as a result of the cooperative effects of gravitational collapse and
nonequilibrium chemistry. Gravity drew the primordial gas together into
lumps; the formation of the first molecules in the universe, simple
diatomic molecules like H_2, H_2+, HD, HeH+, LiH, and
LiH+, were then necessary to
ensure that the heat generated by gravitational
collapse and shock waves was radiated away rapidly enough to allow the
gravitational collapse and fragmentation of these gaseous lumps to
proceed to the point of forming stars and, in some theories, even some of the
galaxies, themselves. Shapiro and his collaborators made several fundamental
contributions to this subject, as summarized in an invited review
by
Shapiro (1992)
for the book Astrochemistry of Cosmic Phenomena
(I.A.U. Symposium 150), including studies of the role of nonequilibrium
H_2 formation and cooling in radiative shocks in the early universe
and in the evolving intergalactic medium (IGM) in the Cold Dark Matter (CDM)
model of cosmology. We describe those which were published in 1992
and later in what follows.