The JWST UNCOVER Treasury survey: Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization

TL;DR

UNCOVER presents a coordinated JWST Treasury program targeting Abell 2744 with ultradeep NIRCam imaging and ultra-deep NIRSpec/PRISM spectroscopy, leveraging strong gravitational lensing to probe the faint, distant galaxy population during the epoch of reionization. The design integrates seven-filter NIRCam imaging and parallel NIRISS data, plus deep spectroscopic follow-up across multiple MSA masks, complemented by extensive ancillary data and a staged, open-data release plan. The project aims to detect and characterize z>10 galaxies, measure rest-frame optical lines and ISM properties, and constrain the role of faint galaxies in reionization, while also exploring dusty and quiescent populations and pushing toward the unknown unknowns. Public data products, including early DR mosaics and lens models, are intended to empower the community for Cycle 2 proposals and beyond, maximizing the scientific return of JWST's early mission.

Abstract

In this paper we describe the survey design for the Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization (UNCOVER) Cycle 1 \JWST Treasury program, which executed its early imaging component in November 2022. The UNCOVER survey includes ultradeep ($\sim29-30\mathrm{AB}$) imaging of $\sim$45 arcmin$^2$ on and around the well-studied Abell 2744 galaxy cluster at $z=0.308$ and will follow-up ${\sim}500$ galaxies with extremely deep low-resolution spectroscopy with the NIRSpec/PRISM during the summer of 2023, with repeat visits in summer 2024. We describe the science goals, survey design, target selection, and planned data releases. We also present and characterize the depths of the first NIRCam imaging mosaic, highlighting previously unparalleled resolved and ultradeep 2-4 micron imaging of known objects in the field. The UNCOVER primary NIRCam mosaic spans 28.8 arcmin$^2$ in seven filters (F115W, F150W, F200W, F277W, F356W, F410M, F444W) and 16.8 arcmin$^2$ in our NIRISS parallel (F115W, F150W, F200W, F356W, and F444W). To maximize early community use of the Treasury data set, we publicly release full reduced mosaics of public JWST imaging including 45 arcmin$^2$ NIRCam and 17 arcmin$^2$ NIRISS mosaics on and around the Abell 2744 cluster, including the Hubble Frontier Field primary and parallel footprints.

Figures (8)

• Figure 1: The UNCOVER combined imaging (purple star) probes a unique regime in the context of HST extragalactic ultradeep fields (blue circles) and JWST Cycle 1 imaging surveys (red squares); without lensing it probes deeper than previous HST surveys and wide field programs. Gravitational lensing (approximate lensing vectors indicated by dashed arrows) from the Abell 2744 allows UNCOVER imaging to probe the intrinsically faintest objects of any JWST project in Cycle 1. We note that lensing vectors are approximate, as the UNCOVER survey includes lensed and unlensed areas of Abell 2744.
• Figure 2: The Abell 2744 cluster has extensive deep optical/NIR (HST and VLT/MUSE) and JWST coverage. The JWST/UNCOVER footprints (purple) along with HST imaging (blue) and VLT/MUSE deep datacube (green, center) and JWST Cycle 1 imaging and spectroscopy (red, right) against imaging from the Legacy Imaging survey dey:19. An updated version with Cycle 2 JWST programs can be found in suess:24. In the left panel, we highlight the detailed layout of the UNCOVER dataset, differentiating between the first epoch (dark purple, NIRCam primary imaging and NIRISS parallel imaging) and second epoch (planned NIRSpec spectroscopy and NIRCam parallel imaging, light purple). The NIRCam mosaic is designed to match the $\mu=2$ magnification curve (see Fig.\ref{['fig:magnification']}). The footprints of the NIRSpec spectroscopy are provisional and subject to target selection.
• Figure 3: Gravitational lensing magnification contours in Abell 2744 are extremely extended, due to the complex structure of the multiple cluster cores. The above curves are taken from the UNCOVER-based lensing model at $z\sim10$furtak:23lensing. The UNCOVER NIRCam mosaic (dark purple) spans the $\mu=2$ curve, which is significantly larger than the Hubble Frontier Field (black dashed outline). By extending to the northern subclumps the UNCOVER mosaic enables a more detailed mapping of that region.
• Figure 4: Top Rows: model SEDs for four key galaxy types and Bottom Rows: Filter curves for deep HST and JWST imaging in the 3 UNCOVER imaging fields. HST imaging (ACS and WFC3) from the Hubble Frontier Field (HFF) program overlaps with the Abell 2744 cluster center (UNCOVER NIRCam primary, top row) and the HFF parallel imaging overlaps with the UNCOVER NIRISS parallel (middle panel). The NIRCam parallel lacks deep optical imaging from HST, but includes F090W and two medium band filters (F335M and F410M).
• Figure 5: Simulated PRISM spectra of a variety of UNCOVER targets , with similar SEDs to those presented in Figure \ref{['fig:filters']}, with total exposure times ranging from 2.7-17.4 hours. The wide wavelength coverage (0.6-5.3 microns) of the NIRSpec/PRISM spectra catch critical spectroscopic features, with a resolution up to $R\sim300$ at the red end. Ultradeep exposures probe the continuum flux for nearly all sources and the multiple mask designs provide spectra for $\sim500-1000$ targets.