Lecture notes for the SAAS-Fee Winter School, April 2006 (to be published by Springer Verlag)
astro-ph/0603360

For a PDF version of the article, click here.

FIRST LIGHT

Abraham Loeb

Department of Astronomy, Harvard University, 60 Garden St., Cambridge, MA 02138 aloeb@cfa.harvard.edu

Abstract. The first dwarf galaxies, which constitute the building blocks of the collapsed objects we find today in the Universe, had formed hundreds of millions of years after the big bang. This pedagogical review describes the early growth of their small-amplitude seed fluctuations from the epoch of inflation through dark matter decoupling and matter-radiation equality, to the final collapse and fragmentation of the dark matter on all mass scales above ~ 10^-4 M. The condensation of baryons into halos in the mass range of ~ 10⁵ - 10¹⁰ M led to the formation of the first stars and the re-ionization of the cold hydrogen gas, left over from the big bang. The production of heavy elements by the first stars started the metal enrichment process that eventually led to the formation of rocky planets and life.

A wide variety of instruments currently under design [including large-aperture infrared telescopes on the ground or in space (JWST), and low-frequency arrays for the detection of redshifted 21cm radiation], will establish better understanding of the first sources of light during an epoch in cosmic history that was largely unexplored so far. Numerical simulations of reionization are computationally challenging, as they require radiative transfer across large cosmological volumes as well as sufficently high resolution to identify the sources of the ionizing radiation. The technological challenges for observations and the computational challenges for numerical simulations, will motivate intense work in this field over the coming decade.

Disclaimer: This review was written as an introductory text for a series of lectures at the SAAS-FEE 2006 winter school, and so it includes a limited sample of references on each subject. It does not intend to provide a comprehensive list of all up-to-date references on the topics under discussion, but rather to raise the interest of beginning graduate students in the related literature.

Table of Contents