Lectures given at the XIII Canary Islands
Winter School of Astrophysics "Cosmochemistry: The
Melting Pot of Elements". Available in electronic form from
http://www.ast.cam.ac.uk/~pettini/canaries13
astro-ph/0303272
For a PDF version of the article, click
here.
For a Postscript version of the article, click
here.
ELEMENT ABUNDANCES THROUGH THE COSMIC AGES
Max Pettini 1
1 Institute of Astronomy,
University of Cambridge
Madingley Road, Cambridge, UK
Abstract. The horizon for studies of element abundances has
expanded dramatically in the last ten years.
Once the domain of astronomers concerned chiefly with stars and
nearby galaxies, this field has now become a key component
of observational cosmology, as technological advances
have made it possible to measure the
abundances of several chemical elements in a variety of environments
at redshifts up to
z 
4, when the
universe was in its infancy. In this series of
lectures I summarise current knowledge on the chemical
make-up of distant galaxies observed directly in
their starlight, and of interstellar and intergalactic gas
seen in absorption against the spectra of bright background sources.
The picture which is emerging is one where the
universe at z = 3 already included many of the constituents
of today's galaxies - even at these early times we see
evidence for Population I and II stars, while the `smoking gun'
for Population III objects may be hidden in the chemical
composition of the lowest density regions of the intergalactic medium,
yet to be deciphered.
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