Revealing the Environment around a Luminous z=6.6 Quasar with JWST
Jaclyn Champagne (Steward Observatory/University of Arizona)
After decades of photometric searches for galaxy overdensities around the luminous z>6 quasars that host 10^9 Msun supermassive black holes, JWST has revolutionized the scene through its wide-field grism capabilities. Now that quasar-anchored overdensities are routinely being uncovered spectroscopically, we can begin to connect our understanding of the earliest protoclusters to their descendant structures at lower redshifts. The JWST ASPIRE program targeted the sightlines of 25 quasars at z=6.5-6.8 with NIRCam imaging and wide-field slitless spectroscopy, efficiently discovering [OIII]+Hb emitting galaxies from z=5.3-7. Here I present the first detailed joint spectroscopic and imaging analysis of the richest protocluster candidate among these quasars using JWST + ALMA data. We examine the effect of the overdense environment on the evolution of galaxies within the filamentary overdensities, with particular attention to the difficulties in selecting AGN among the [OIII] emitters. In addition to a tentative overdensity of ``little red dots" with high [OIII]/Hb, we also find systematically suppressed specific star formation rates and older stellar population ages for galaxies situated in the densest filaments. I will also discuss the potential effects of photoionization from the central quasar within the proximity zone on the evolution of protocluster galaxies in its immediate environment.
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