Astronomy Colloquium

The first 400 Myr of cosmic history are extremely challenging to model and observe, but at the same time are also deeply important to understand since some of the crucial events in cosmic history, such as the formation of the very first stars, took place in that time window. Perhaps the most promising way to fill in the missing pages of cosmic history is by detecting the 21-cm signal of neutral hydrogen emitted by the intergalactic medium. This signal is predicted to be observable by the upcoming generation of radio telescopes, and, being correlated to the radiation emitted by stars and quasars, it can tell us a great deal about the epoch of Reionization and Cosmic Dawn. In this talk I will discuss theoretical modeling of the 21-cm signal, expand on its properties, and outline what can be learned from this signal about the early Universe, focusing on the nature of the first heating sources.