For ``Physics Reports'' special issue in memory of D.N. Schramm; (astro-ph/9912345)


`FIRST LIGHT' IN THE UNIVERSE;
WHAT ENDED THE "DARK AGE"?

Martin J. Rees


Institute of Astronomy
Madingley Road, Cambridge, CB3 0HA, United Kingdom
mjr@ast.cam.ac.uk


Abstract. The universe would have been completely dark between the epoch of recombination and the development of the first non-linear structure. But at redshifts beyond 5 - perhaps even beyond 20 - stars formed within `subgalaxies' and created the first heavy elements; these same systems (together perhaps with `miniquasars') generated the UV radiation that ionized the IGM, and maybe also the first significant magnetic fields. Although we can already probe back to z appeq 5, these very first objects may be so faint that their detection must await next-generation optical and infrared telescopes. Observations in other wavebands may offer indirect clues to when reionization occurred. Despite the rapid improvements in numerical simulations, the processes of star formation and feedback are likely to remain a challenge for the next decade.


Table of Contents

INTRODUCTION

COSMOGONIC PRELIMINARIES: MOLECULAR HYDROGEN AND UV FEEDBACK
The H2 Cooling Regime
The Atomic-Cooling Stage

THE EPOCH OF IONIZATION BREAKTHROUGH
UV Production in `Subgalaxies'
How Uncertain is the Ionization Epoch?
Detecting `Pregalaxies' at Very High Redshift
The `Breakthrough' Epoch
Black Hole Formation and AGNs at High z?
Distinguishing Between Objects with z > zi and z < zi

RADIO AND MICROWAVE PROBES OF THE IONIZATION EPOCH
CMB Fluctuations as a Probe of the Ionization Epoch
21 cm Emission, Absorption and Tomography

VERY DISTANT SUPERNOVAE (AND PERHAPS GAMMA-RAY BURSTS)
The Supernova Rate at High Redshifts
Gamma Ray Bursts: The Most Luminous Known Cosmic Objects

WHERE ARE THE OLDEST (AND THE EXTREME METAL-POOR) STARS?

SUMMARY

REFERENCES

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