Joint Astrophysics Colloquium

Joint Astrophysics Seminar

Probing the End of the Cosmic Dark Age

Zoltan Haiman

Columbia University

I the currently favored cosmological paradigm, the first non-linear objects are small dark matter halos that formed at redshift z ~ 30. The pristine primordial gas in these halos can dissipate its energy by excitations of molecular hydrogen, and contract to high densities to form the first generation of stars and black holes. These objects subsequently evolve into the population of well-studied galaxies and quasars at redshift z<6. The first stars and black holes can have a significant impact on the rest of the universe as soon as they appear, by photo-ionizing most of the baryons. The cosmic microwave background anisotropies (measured by the Wilkinson Microwave Anisotropy Probe), and the spectra of the most distant quasars (discovered in the Sloan Digital Sky Survey), have recently provided the first glimpses of the early ionization history of the universe. I will discuss plausible interpretations of these recent observations. In the next decade, new instruments should characterize the ionization history and tomography in detail, and allow us to infer the abundance, spectrum, and other properties of the first generation of astrophysical objects.