The Light Echo of a High-Redshift Quasar mapped with Lyman-alpha Tomography

The ultraviolet radiation of luminous high-redshift quasars within the Epoch of Reionization carves out large bubbles of highly ionized intergalactic gas in the quasars' environments, making the otherwise opaque Lyman-alpha forest highly transparent at redshifts near the quasar. I will present the first results from the JWST MASQUERADE program, which leverages some of the deepest NIRSpec/MSA observations to date of galaxies in the background and environment of luminous quasars at z>6 to tomographically map the quasars' ionized bubbles, enabling a unique opportunity to probe the AGN unification model at early cosmic times. The extents of these bubbles provide model-independent constraints on the quasars' ages based on the light travel time, providing new insights on the puzzle of the early growth of supermassive black holes. Simultaneously, the quasars' highly ionized regions represent a unique laboratory to study the intrinsic ionizing properties and unattenuated line profiles of high-redshift galaxies without absorption by the neutral intergalactic medium to reveal the elusive protagonists that reionize the universe.