Invited review, Ringberg Workshop: "Galaxies in the
Young Universe II", Aug. 2-6 1999, Hans Hippelein (ed.),
Springer-Verlag;
For a postscript version of the article, click
here.
astro-ph/9911204
Abstract. Initial conditions are set by Big bang nucleosynthesis
from which we know
that 90 per cent of baryons are dark and have essentially unknown chemical
composition. In our own Galaxy, there are many clues from individual
stars in different populations whereas in elliptical galaxies the data
largely come
from integrated spectra, but these raise problems enough like the Mg/Fe
and G-dwarf problems. Irregular and blue compact galaxies display
the primary-secondary transition in
N/O; this in turn may be relevant to element ratios observed in damped
Lyman-
systems at high
red-shift, which offer rather little evidence
for pure SNII synthesis such as is found in the Galactic halo stars. A
recent estimate of past star formation rates as a function of red-shift
is presented
and the appropriateness of the conventional conversion factor of 42 from
SFR to metal production is discussed. For any reasonable value of this
conversion factor, it is clear that most of the metals existing at
z = 2.5 have yet to be detected.
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