Probing Cosmic Reionization with Quasar Proximity Zones

Huanqing Chen (CITA)

October 17, 2022

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Abstract: In the first billion years of the Universe, the first galaxies and quasars formed and their ionizing photons brought about a major phase transition of the IGM from a mostly neutral to a mostly ionized state. The exploration of this crucial epoch, called cosmic reionization, is entering a golden era with the exponential progress in computational ability and with JWST and 30m-class telescopes on the horizon. The regions around the first quasars, called quasar proximity zones, are among the first targets that JWST will observe. They are unique since they are thought to trace the densest environments where many galaxies reside. Besides, the quasar spectra carry rich information about the IGM during reionization. In this talk, I will show multiple aspects of what we can learn from the quasar proximity zones. First, I will show how to interpret the size of observed proximity zones and how to use the absorption features to recover the density and further constrain cosmology and quasar properties. Second, I will talk about my suite of quasar proximity zone simulations and show how galaxies form in this biased field with strong radiation. This study will help us interpret future JWST data and answer key questions about the quasar environment and radiative feedback. I will conclude with an outlook of synergizing JWST and ground-based observations of quasar proximity zones to learn more about reionization.