The JWST FRESCO survey: legacy NIRCam/grism spectroscopy and imaging in the two GOODS fields

P. Oesch et al., incl. C. Neufeld (2023)

Abstract | ADS link

We present the JWST cycle 1 53.8 h medium program FRESCO, short for ‘First Reionization Epoch Spectroscopically Complete Observations’. FRESCO covers 62 arcmin2 in each of the two GOODS/CANDELS fields for a total area of 124 arcmin2 exploiting JWST’s powerful new grism spectroscopic capabilities at near-infrared wavelengths. By obtaining ~2 h deep NIRCam/grism observations with the F444W filter, FRESCO yields unprecedented spectra at R ~ 1600 covering 3.8-5.0 µm for most galaxies in the NIRCam field of view. This setup enables emission line measurements over most of cosmic history, from strong PAH lines at z ~ 0.2-0.5, to Pa α and Pa β at z ~ 1-3, He I and [S III] at z ~ 2.5-4.5, H α and [N II] at z ~ 5-6.5, up to [O III] and H β for z ~ 7-9 galaxies. FRESCO’s grism observations provide total line fluxes for accurately estimating galaxy stellar masses and calibrating slit-loss corrections of NIRSpec/MSA spectra in the same field. Additionally, FRESCO results in a mosaic of F182M, F210M, and F444W imaging in the same fields to a depth of ~28.2 mag (5σ in 0.32" diameter apertures). Here, we describe the overall survey design and the key science goals that can be addressed with FRESCO. We also highlight several, early science results, including: spectroscopic redshifts of Lyman break galaxies that were identified almost 20 yr ago, the discovery of broad-line active galactic nuclei at z > 4, and resolved Pa α maps of galaxies at z ~ 1.4. These results demonstrate the enormous power for serendipitous discovery of NIRCam/grism observations.