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

Rachel Bezanson, Ivo Labbé+41 more|arXiv (Cornell University)|Dec 8, 2022

Astronomy and Astrophysical ResearchPhysics and Astronomy37 citations

TL;DR

The paper outlines the UNCOVER JWST Treasury program design, detailing ultradeep NIRCam imaging and NIRSpec/PRISM spectroscopy around Abell 2744, plus data-release plans and expected galaxy counts.

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.

Motivation & Objective

• Motivate study of the first galaxies and cosmic reionization through ultradeep, lensing-enhanced JWST observations.
• Describe the UNCOVER survey design, including imaging and spectroscopy, field selection, and target prioritization.
• Outline data reduction, public data releases, and ancillary datasets to maximize community use.

Proposed method

• Propose an imaging-first strategy with deep NIRCam pre-imaging (7 filters) and ultra-deep NIRSpec/PRISM spectroscopy targeting NIRCam-detected high-z galaxies.
• Leverage Abell 2744 gravitational lensing to push intrinsic depths beyond blank-field capabilities.
• Use Grizli-based reduction to create calibrated, co-added mosaics and PSF-matched catalogs.
• Plan seven NIRSpec MSA masks with exposure times ranging from 2.77 to 19.4 hours, plus 0.6–5.3 μm spectral coverage.
• Publicly release reduced NIRCam/NIRISS mosaics and evolving data products to enable broad community use.

Experimental results

Research questions

• RQ1 What are the expected ultradeep imaging depths in the UNCOVER NIRCam/NIRISS mosaics and how do they translate to detections of z>6–10 galaxies?
• RQ2 How does gravitational lensing in Abell 2744 enhance the survey's ability to probe intrinsically faint, high-redshift galaxies?
• RQ3 What are the anticipated yields of high-z candidates and other target classes (dusty star-forming, quiescent, AGN) in UNCOVER?
• RQ4 What is the planned timeline and content of public data releases (DR1, DR2, DR3) for UNCOVER components?

Key findings

• UNCOVER achieves ultradeep imaging depths around 30 AB mag (5σ) in multiple NIRCam filters across ~28.8 arcmin^2 of primary imaging and 16.8 arcmin^2 of NIRISS parallel imaging.
• NIRCam pre-imaging depths reach ~30 AB mag in F115W, F150W, F200W, F277W, F356W, F410M, F444W (and ~29 AB in some bands), enabling detection of galaxies at z>10 with lensing aid.
• NIRSpec/PRISM spectroscopy (0.6–5.3 μm, R~30–300) will obtain ultradeep spectra to measure continuum redshifts and emission lines for ~500–1000 targets across seven MSA mask configurations.
• Predicted counts for target classes include ~36 lensed z>12 candidates and ~9 in parallel; ~1,500 galaxies at 6≲z≲7 in both fields; dozens of dusty and quiescent galaxies at z>1–>3 (per Table 2).
• A comprehensive data-release plan is outlined (DR1 imaging mosaics and lens model, DR2 photometric catalogs, DR3 reduced PRISM spectra and derived properties) to maximize community use.