Probing Cosmic Reionization with Quasar Proximity Zones

Probing the epoch of reionization, which happened in the first billion years of the Universe, is an exciting research frontier of modern astrophysics and cosmology. Observing reionization is challenging, due to the saturation of Lya absorption of distant quasars and the scarceness of observable galaxies. However, the quasar proximity zones are ideal windows to study reionization: the enhanced radiation field reduces the saturation in Lya absorption, allowing us to delve into the details of IGM properties. Moreover, quasars are thought to reside in most massive halos, around which more galaxies than average form. At the same time, the radiation feedback from the quasar mimics the radiation feedback of cosmic reionization. Therefore, the study of quasar fields helps us to understand the feedback of cosmic reionization on galaxies. In this talk, I will show two highlights of my research: how to recover the density field in quasar proximity zones and how the radiation feedback from a quasar impacts galaxy formation. I will conclude my talk with a discussion of new exciting science we can do using quasar proximity zones. In the near future, data from JWST and thirty-meter class telescopes will revolutionize our understanding of the epoch of reionization and the formation of the first quasars/galaxies.