Reionization and Cosmic Dawn: theory and simulations

Understand

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.