Reionization and Cosmic Dawn: theory and simulations
  We highlight recent progress in the sophistication and diversification of
cosmic dawn and reionization simulations. The application of these modeling
tools to current observations has allowed us narrow down the timing of
reionization, which we now know to within dz ~ 1 for the bulk of reionization.
The strongest constraints come from the optical depth to the CMB measured with
the {\it Planck} satellite and the first detection of ongoing reionization from
the spectra of the z=7.1 QSOs ULASJ1120+0641. However, we still know virtually
nothing about the astrophysical sources during the first billion years. The
revolution in our understanding will be led by upcoming interferometric
observations of the cosmic 21-cm signal. The properties of the sources and
sinks of UV and X-ray photons are encoded in the 3D patterns of the signal. The
development of Bayesian parameter recovery techniques, which tap into the
wealth of the 21-cm signal, will soon usher in an era of precision
astrophysical cosmology.
