During the Epoch of Reionization (EoR) primeval galaxies and accreting black holes reionized and reheated the hydrogen in the intergalactic medium (IGM) ending the preceding cosmic `dark ages'. Understanding how reionization occurred and the nature of the early sources that drove it are among the most important open questions in cosmology. The latest cosmic microwave background constraints suggest reionization occurred at z ~ 7-8, within the realm of the highest redshift quasars known. I will argue that the discovery of bright quasar beacons in a neutral IGM enables a set of qualitatively new absorption spectroscopy experiments which can teach us about reionization, supermassive black hole growth, and early cosmic enrichment. Current constraints based on ground based spectra of the handful of known z > 7 quasars will be presented. But this is only scratching the surface -- the successful launch of JWST in 2021 and imminent launch of the ESA/Euclid mission will deliver exquisite data for over a hundred quasars deep into the EoR transforming our knowledge of the high redshift universe.
Topic: Astronomy Colloquium SP22
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Meeting ID: 898 8024 2486