16667

Despite the success of galaxy formation models comma some questions remain largely unanswered. Chief among thesedoublePoint (1) how did galaxies reionize the universe (if they did)questionMark (2) How do they evolvequestionMark (3) How do gas and metals cycle in and out of galaxiesquestionMark JWST will undoubtedly help us advance galaxy formation and evolution science. However comma to answer these and many other questions comma deep rest-frame UV and optical data will still be required. Given JWST.s limited lifetime comma it is essential to obtain ancillary data crucial for its success. The JWST GTO program CANUCS (CAnadian NIRISS Unbiased Cluster Survey) aims to answer these questions by observing five galaxy clusters and ten parallel fields for 200 hours with NIRISS grisms comma NIRCam imager comma and NIRSpec multi-object spectrograph. However comma only in conjunction with the proposed deep comma high-resolution optical data will it determinedoublePoint (1) Lyman-alpha observability of a sample of >1000 galaxies at z > 6 well into the reionization epoch. (2) Robustly determine star formation histories of >10 comma 000 cosmic-noon galaxies. (3) Study metallicity gradients of >200 dwarf galaxies in a large and well-defined sample at cosmic noon. This proposal will deliver uniform and essential data using ACS F435W and F606W for the CANUCS clusters comma perform a supernova search and explore extraordinary objects comma including a galaxy similar to the host of supernova Refsdal and an intrinsically faint comma low-mass confirmed z>7 source. This proposal will provide an extremely valuable data set for the whole community comma and we waive any proprietary rights for this proposal.