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

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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 Modot. The condensation of baryons into halos in the mass range of ~ 105 - 1010 Modot 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

OPENING REMARKS

EXCAVATING THE UNIVERSE FOR CLUES ABOUT ITS HISTORY

BAKGROUND COSMOLOGICAL MODEL
The Expanding Universe
Composition of the Universe
Linear Gravitational Growth
The Smallest-Scale Power Spectrum of Cold Dark Matter
Structure of the Baryons
Formation of Nonlinear Objects
Spherical Collapse
Halo Properties

NONLINEAR GROWTH
The Abundance of Dark Matter Halos
The Excursion-Set (Extended Press-Schechter) Formalism
Response of Baryons to Nonlinear Dark Matter Potentials

FRAGMENTATION OF THE FIRST GASEOUS OBJECTS TO STARS
Star Formation
The Mass Function of Stars
Gamma-ray Bursts: Probing the First Stars One Star at a Time
Emission Spectrum of Metal-Free Stars
Emission of Recombination Lines from the First Galaxies

SUPERMASSIVE BLACK HOLES
The Principle of Self-Regulation
Feedback on Large Intergalactic Scales
What seeded the growth of the supermassive black holes?

RADIATIVE FEEDBACK FROM THE FIRST SOURCES OF LIGHT
Escape of Ionizing Radiation from Galaxies
Propagation of Ionization Fronts in the IGM
Reionization of Hydrogen
Photo-evaporation of Gaseous Halos After Reionization
Suppression of the Formation of Low Mass Galaxies

FEEDBACK FROM GALACTIC OUTFLOWS
Propagation of Supernova Outflows in the IGM
Effect of Outflows on Dwarf Galaxies and on the IGM

THE FRONTIER OF 21CM COSMOLOGY
Mapping Hydrogen Before Reionization
The Characteristic Observed Size of Ionized Bubbles at the End of Reionization
Separating the "Physics" from the "Astrophysics" of the Reionization Epoch with 21cm Fluctuations

MAJOR CHALLENGE FOR FUTURE THEORETICAL RESEARCH: radiative transfer during reionization requires a large dynamic range, challenging the capabilities of existing simulation codes

REFERENCES

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