The first billion years

The development of primordial inhomogeneities into the non-linear regime and the formation of the first astrophysical objects within low-mass (M ∼ 106 M⊙) dark matter halos mark the end of the cosmic dark ages, about 150 Myr after the big bang. It is an early generation of extremely metal-poor stellar systems and accreting black holes in their nuclei that generated the ultraviolet/soft X-ray radiation and mechanical energy that reheated and reionized most of the hydrogen in the cosmos. The detailed thermal, ionization, and chemical enrichment history of the universe during the crucial formative stages around z = 10 - 30 depends on the power-spectrum of density fluctuations on small scales, on gas-phase H2 " astrochemistry", the stellar initial mass function and star formation efficiency, a complex network of poorly understood "feedback" mechanisms, and remains one of the crucial missing links in galaxy formation and evolution studies. In this talk I will review recent progress in understanding the epoch of first light, the impact of the earliest generation of luminous objects on later ones, and the hierarchical assembly of massive black holes from Population III seeds.