Joint Astrophysics Colloquium

Constraining the history of reionization with quasar absorption lines

Laura Keating

Leibniz Institute for Astrophysics Potsdam

The epoch of reionization marks the last major phase transition of the Universe, when photons emitted by the first structures ionized and heated the gas surrounding them. A complete understanding of reionization would reveal the properties of the first stars and galaxies, as well as increasing the precision to which the high-redshift intergalactic medium can be used as a cosmological probe. In this talk I will present results from radiative transfer simulations of cosmic reionization and compare them with observations of the Lyman-alpha forest, the pattern of absorption lines observed in quasar spectra. I will show that matching the observed statistics of the Lyman-alpha forest requires reionization to have ended later than previously thought, with islands of neutral hydrogen still found below redshift 5.5. Finally, I will show how this late reionization scenario could impact other reionization observables.