James Webb Space Telescope Feed Post

The JWST FRESCO Survey: Legacy NIRCam/Grism Spectroscopy and Imaging in the two GOODS Fields Published: 4/4/2023 9:00:00 PM Updated: 8/16/2023 11:07:07 AM

Paper abstract: We present the JWST Cycle 1 53.8hr medium program FRESCO, short for "FirstReionization Epoch Spectroscopically Complete Observations". FRESCO covers 62arcmin^2 in each of the two GOODS/CANDELS fields for a total area of 124arcmin^2 exploiting JWST's powerful new grism spectroscopic capabilities atnear-infrared wavelengths. By obtaining ~2 hr deep NIRCam/grism observationswith the F444W filter, FRESCO yields unprecedented spectra at R~1600 covering3.8 to 5.0 \mum for most galaxies in the NIRCam field-of-view. This setupenables emission line measurements over most of cosmic history, from strong PAHlines at z~0.2-0.5, to Pa\alpha and Pa\beta at z~1-3, HeI and [SIII] atz~2.5-4.5, H\alpha and [NII] at z~5-6.5, up to [OIII] and H\beta for z~7-9galaxies, and possibly even [OII] at z~10-12. FRESCO's grism observationsprovide total line fluxes for accurately estimating galaxy stellar masses andcalibrating slit-loss corrections of NIRSpec/MSA spectra in the same field.Additionally, FRESCO results in a mosaic of F182M, F210M, and F444W imaging inthe same fields to a depth of ~28.2 mag (5 \sigma in 0.32" diameterapertures). Together with this publication, the v1 imaging mosaics are releasedas high-level science products via MAST. Here, we describe the overall surveydesign and the key science goals that can be addressed with FRESCO. We alsohighlight several, early science results, including: spectroscopic redshifts ofLyman break galaxies that were identified almost 20 years ago, the discovery ofbroad-line active galactic nuclei at z>4, and resolved Pa\alpha maps ofgalaxies at z~1.4. These results demonstrate the enormous power forserendipitous discovery of NIRCam/grism observations.