First Light In The Universe: Probing the End Of The Dark Ages

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

AST 0205738 Madau In currently popular cosmological scenarios at very early times, the gas within protogalactic halos with masses comparable to those of present-day dwarf ellipticals experienced rapid cooling and fragmentation. These fragments formed massive stars , which in turn synthesized heavy elements, and exploded as Type II supernovae, enriching the surrounding medium. These subgalactic stellar systems then generated the ultraviolet radiation and mechanical energy that reheated and reionized most of the hydrogen in the cosmos. The history of the Universe during and soon after these crucial formative stages is recorded in the thermal state, ionization degree, and chemical composition of the all-pervading intergalactic medium (IGM). Throughout the epoch of structure formation, the IGM becomes clumpy under the influence of gravity, and acts as a source for the gas that accretes, cools, and forms stars within subgalactic fragments, and as a sink for the metal enriched material, energy, and radiation which they eject. The study of the gaseous and stellar content of the high-redshift Universe thus provides invaluable insight into this era and the basic processes that govern the collapse, cooling, and evolution of some of the earliest formed cosmological structures. This theoretical project will study the epoch of .first light, the astrophysics of protogalactic systems, the intergalactic medium and quasar absorbers in the context of current theories of galaxy formation. It will focus on a series of critical questions in each of these interrelated areas: (1) cosmological reionization, (2) the epoch of first light, and (3) protogalaxy halos, SN-driven winds, and the metal enrichment of the IGM. A coordinated approach will be pursued involving theoretical studies of the controlling physical processes, and direct numerical simulation of their effects within the current paradigm for structure formation. The results of this program should aid in the planning for future large observational facilities such as the California Extremely Large Telescope, the Low Frequency Array, the Square Kilometer Array, and the Next Generation Space Telescope. ***