Cosmic reionisation and the first stars

Thurs 1st Aug 2019 @14:15 PM, level 7, David Caro Building
Adélie Gorce Imperial College London/Institut d’Astrophysique Spatiale



During the Epoch of Reionisation (EoR), the first galaxies and AGNs ionise the neutral atoms surrounding them. Although essential, this period in the history of the Universe is still poorly known. We wonder about the sources: if it is generally admitted that the first stars led the process, more exotic sources such as the bright radiation of quasars might be needed. But also about the chronology: when were the first stars born? How efficient were they to ionise the IGM, what were their properties? Finally, about the topology: were overdense regions ionised first or last?…

In this talk, I’ll give an overview of the different observational ways available to learn about cosmic reionisation, from astrophysics to cosmology, from galaxy and quasar spectra to the 21cm signal. I’ll present the assumptions usually made to model reionisation and how they can impact the interpretation of observations. Finally, I’ll spend some time on the prospects of observing the 21cm signal to learn about the EoR, and in particular, what we can learn from the non-Gaussianity of the signal.