Context

Theoretical models generically predict that luminous z>6 quasars should reside in the most massive dark matter halos at these early times, and are signposts for large overdensities of galaxies. However, despite nearly two decades of searching these overdensities around quasars have never been convincingly detected. The main reason is that previous studies solely relied on broad band selection of Lyman break galaxies (LBGs) in quasar fields and the overdensity signals were significantly diluted by the large uncertainty of photometric redshifts of the LBGs. To solve this difficulty, we will use a series of narrow band filters to select Lyman alpha emitters (LAEs) in well selected quasar fields with Magellan/IMACS, Subaru/HSC and HST/WFC3. This program will provide a definitive answer to the long-standing open question: whether the most massive supermassive black holes (SMBHs) in the early Universe inhabit large overdensities of galaxies, and thus reside in the most biased dark matter halos. The narrow band observations will also detect close companion galaxies and the extended Lyman alpha halos around the quasars to pinpoint whether the fast black hole growth are triggered by galaxy merger or cold stream accretion. More details will come soon.