Abstract

The existence of luminous quasars, powered by billion-solar-mass supermassive black holes (SMBHs), when the Universe was less than 800 million years old, challenges our understanding of SMBH formation. In the context of hierarchical structure formation, an assortment of cosmological simulations can produce these massive SMBHs, starting with massive seeds. These models generically predict that the earliest quasars are hosted by massive galaxies and reside in the most biased dark matter halos situated in overdense regions. However, rigorously testing these theories remains challenging. To address this challenge, I developed the ASPIRE program, which provides a legacy galaxy redshift survey along the lines of sight of distant quasars with extensive observations from JWST, ALMA, Chandra, HST, VLA, and ground-based optical and infrared instruments. In this talk, I will demonstrate that we are now finally able to test these theories in detail by probing the multi-scale environment of the earliest SMBHs and resolving the long-standing questions of whether these SMBHs reside in massive galaxies and whether they are hosted by biased dark matter halos. I will highlight ASPIRE as a treasury program for understanding cosmic reionization, galaxy formation, and metal enrichment in the early Universe. Finally, I will illustrate that we are entering an exciting new era in our understanding of the formation of early SMBHs and galaxies in a cosmological context and the process of cosmic reionization, leveraging the unprecedented sensitivity of JWST, along with upcoming state-of-the-art facilities such as Euclid, Roman, Rubin, and GMT.