JADES Data Release 4 Paper I: Sample Selection, Observing Strategy and Redshifts of the complete spectroscopic sample

TL;DR

DR4 delivers the complete JWST/JADES NIRSpec spectroscopic dataset for GOODS-N and GOODS-S, enabling robust redshift measurements for thousands of galaxies up to z ≳ 14 across 0.8–5.5 μm. The paper details the tiered observing strategy, target-selection framework, and redshift-validation process, and introduces two homogeneous gold samples to facilitate population-level analyses. By constructing rest-UV luminosity functions in the z ≈ 6–9 range and validating photometric redshift selections against spectroscopic redshifts, the work demonstrates the reliability of JWST-based high-redshift galaxy studies and provides a legacy dataset for galaxy evolution across cosmic time. Together with DR4_paper2, this release substantiates JWST’s capability to push the redshift frontier and to assemble the largest, most comprehensive spectroscopic census of early galaxies to date.

Abstract

This paper accompanies Data Release 4 of the JWST Deep Extragalactic Survey (JADES), which presents the full NIRSpec spectroscopy of the survey. We provide spectra of 5190 targets across GOODS-North and GOODS-South (including the Hubble Ultra Deep Field), observed with the low-dispersion (R $\sim$ 30-300) prism and three medium-resolution (R $\sim$ 1000) gratings spanning 0.8 $< λ<$ 5.5 microns; 2654 were also observed with the higher-resolution (R $\sim$ 2700) G395H grating. The tiered survey design obtained more than 20 hr exposures for $\sim$ 700 galaxies in the Deep and Ultra Deep tiers, and shallower observations ($\sim$ 1-3 hr per setting) of $>$ 4400 galaxies in the Medium tiers. Targets were selected from photometric redshifts or colours, with priority given to rest-UV-selected galaxies at $z > 5.7$ and F444W-selected galaxies at $1.5 < z < 5.7$. We describe the full target selection and present spectroscopic redshifts and success rates. In total we obtain robust redshifts for 3297 galaxies, including 396 at $z > 5.7$ and 2545 at $1.5 < z < 5.7$. To facilitate uniform analyses, we define 'gold' sub-samples based on UV- and F444W-selection. Using the parent samples and redshift success rates, we construct rest-UV luminosity functions at $6 \lesssim z \lesssim 9$ from the Medium- and Deep-JWST tiers. Our number densities agree well with previous determinations from both photometric and spectroscopic samples, with modest interloper fractions confirming the reliability of photometric UV-bright galaxy selections at these redshifts.

Figures (10)

• Figure 1: Timeline of the JADES survey footprint in GOODS-South. The grey outline shows the coverage of pre-existing HST data in the WFC3 F160W filter taken from the Hubble Legacy Fields Whitaker2019. The Green rectangle and plus sign indicate the outline and central position of the Hubble eXtreme Deep Field Illingworth2013. The filled grey regions show the JADES NIRCam data available for NIRSpec target selection undertaken within the time-frame indicated at the top of each panel. NIRSpec pointings taken within the same time-frame are shown with the shading set by the Tier, as indicated in the legend. The regions for each pointing cover the useable NIRSpec MSA area that avoids truncated PRISM spectra, and indicate the area of the MSA used for target allocation. The Medium/JWST pointings in the Oct 2022 - Jan 2023 (left) panel indicate the early goods-s-mediumjwst pointings that constitute the subsample labelled 'GSa', while the Medium/JWST pointings in the Sep - Dec 2023 (central) panel constitute the goods-s-mediumjwst pointings referred in the text as 'GSb' (see Section \ref{['sec:target_selection']} for more details).
• Figure 2: As for Figure \ref{['fig:footprint_gs']}, but showing the timeline of the JADES survey footprint in GOODS-North. As in the previous figure, the grey outline represents the footprint of prior HST WFC3 F160W observations combined by Illingworth2017
• Figure 3: Histogram of exposure times from the full JADES survey. The top panel shows exposure times from the "Medium" tiers (see text for description). The green solid line shows exposures in the Prism/Clear mode. Pink dashed line shows the exposure time in each medium resolution ($R\sim1000$) gratings (note that these targets received the given exposure time in each of G140M/F070LP, G235M/F170LP, G395M/F290LP to cover the full wavelength range). The cyan dotted line shows the exposure time in the high resolution ($R\sim2700$) grating G395H/F290LP. The lower panel shows the same, but for the JADES "Deep" tiers where for goods-s-ultradeep, the $R\sim1000$ grating observations are only taken with G395M/F290LP.
• Figure 4: Layout of Medium/JWST pointings in GOODS-S across the two main epochs, GSa (purple; prior to Sep 2023) and GSb (orange; after Sep 2023). Shaded regions within MSA footprints show areas where NIRCam imaging was not available when target selection was performed for the observation in question. Dark blue points show our nomimal priority classes (PC) = 1&2 targets (with $z>8$), used to set the pointing centres. After the original pointings in GSa, there were very few unobserved PC=1 & 2 targets in the northern part of the field, leading us to supplement these with F090W-dropout selected galaxies, which have $z\gtrsim6.5$ (Class 2d in Table \ref{['tab:priorities_Medium_JWST']}; light blue circles). In addition, candidate members of a $z\approx7.3$ overdensity, identified from medium-band excesses (Class 1x in Table \ref{['tab:priorities_Medium_JWST']}; teal crosses) were added to the top priority classes in some GSa pointings.
• Figure 5: A selection of high-quality emission-line spectra from this Data Release, sorted by redshift. Numerous emission line and continuum features are clearly visible, showcasing the richness of the dataset.