FRESCO: The First Reionization Epoch Spectroscopic COmplete Survey
Revealing the dramatic build-up of galaxies during the first 1 billion years to the peak of star formation at z~2-3 is one of Hubble's greatest achievements. Yet huge gaps in our understanding remain since our galaxy samples are incomplete due to the uncertainties of photometric selection. The highly-incomplete spectroscopic information at z>6 means that we lack physical understanding of the processes driving early galaxy assembly. To date, less than 1% of known galaxies in the epoch of reionization at z>6 have confirmed redshifts, and basic quantities such as mass-to-light ratios can be uncertain by factors of 5-10 — due to the unknown contributions of strong emission lines in the photometry used to derive stellar masses. As a result, we still only have a broad, phenomenological picture of early galaxy formation and growth. FRESCO exploits JWST's remarkable new spectroscopic capabilities to remedy this situation in a maximally-efficient way. By obtaining 2 hr deep NIRCam/grism observations with just the F444W filter, FRESCO will yield redshifts over a wide redshift range for a complete sample of ~330 z~7-9 galaxies, as well as ~1200 z~5-6.5 galaxies, in the Deep CANDELS areas of the GOODS-S and GOODS-N fields. FRESCO will yield an unprecedented Legacy archive, for the first time, of spectroscopic redshifts and emission line measurements from [OIII]+H-beta, H-alpha, and even Pa-alpha at low redshifts. FRESCO's grism observations provide the total line fluxes for estimating galaxy stellar mass and critically-needed slit-loss calibrations of NIRSpec/MSA spectra. We are not requesting proprietary time to ensure that FRESCO will be a key Legacy dataset for the community.
PI: Pascal Oesch
CoIs: Gabe Brammer, Rychard Bouwens, John Chisholm, Yoshi Fudamoto, Garth Illingworth, Josie Kerutt, Ivo Labbe, Dan Magee, Danilo Marchesini, Michael Maseda, Charlotte Mason, Rohan Naidu, Erica Nelson, Yuxiang Qin, Naveen Reddy, Daniel Schaerer, Alice Shapley, Irene Shivaei, Renske Smit, Mauro Stefanon, Kate Whitaker, Stijn Wuyts, Stuart Wyithe, Pieter van Dokkum