Studying the formation and evolution of galaxies at the earliest cosmic times, and their role in reionization, requires the deepest imaging possible. Ultra-deep surveys like the HUDF and HFF have pushed to mag mAB ∼ 30, revealing galaxies at the faint end of the LF to z ∼ 9 − 11 and constraining their role in reionization. However, a key limitation of these fields is their size, only a few arcminutes (less than a Mpc at these redshifts), too small to probe large-scale environments or clustering properties of these galaxies, crucial for advancing our understanding of reionization. Achieving HUDF-quality depth over areas ∼100 times larger becomes possible with a mission like the Wide Field Infrared Survey Telescope (WFIRST), a 2.4-m telescope with similar optical properties to HST, with a field of view of ∼1000 arcmin2, ∼100× the area of the HST/ACS HUDF. This whitepaper motivates an Ultra-Deep Field survey with WFIRST, covering ∼100 − 300× the area of the HUDF, or up to ∼1 deg2, to mAB ∼ 30, potentially revealing thousands of galaxies and AGN at the faint end of the LF, at or beyond z ∼ 9 − 10 in the epoch of reionization, and tracing their LSS environments, dramatically increasing the discovery potential at these redshifts.
|Original language||English (US)|
|State||Published - Mar 14 2019|
ASJC Scopus subject areas