JADES NIRSpec Initial Data Release for the Hubble Ultra Deep Field: Redshifts and Line Fluxes of Distant Galaxies from the Deepest JWST Cycle 1 NIRSpec Multi-Object Spectroscopy

TL;DR

The paper presents the JADES NIRSpec initial data release, detailing extremely deep MOS spectroscopy in the HUDF/GOODS-South fields and public release of reduced spectra and emission-line redshift catalogs. It describes target selection leveraging NIRCam/HST photometry, MOS mask design with the eMPT tool, three-pointing observations across prism and multiple gratings, and a careful data-reduction pipeline. Redshifts are measured up to z=13.2 with robust line detections (S/N>5) for many objects, enabling insights into the distant infrared universe and ISM properties; the results validate the high-yield target-prioritization strategy (~80% success) and demonstrate the power of JWST/NIRSpec MOS for exploring galaxy evolution across cosmic time. The public data release of deep spectra and line fluxes establishes a foundational dataset for community-driven exploration of high-redshift galaxies and their physical conditions.

Abstract

We describe the NIRSpec component of the JWST Deep Extragalactic Survey (JADES), and provide deep spectroscopy of 253 sources targeted with the NIRSpec micro-shutter assembly in the Hubble Ultra Deep Field and surrounding GOODS-South. The multi-object spectra presented here are the deepest so far obtained with JWST, amounting to up to 28 hours in the low-dispersion ($R\sim 30-300$) prism, and up to 7 hours in each of the three medium-resolution $R\approx 1000$ gratings and one high-dispersion grating, G395H ($R\approx2700$). Our low-dispersion and medium-dispersion spectra cover the wavelength range $0.6-5.3μ$m. We describe the selection of the spectroscopic targets, the strategy for the allocation of targets to micro-shutters, and the design of the observations. We present the public release of the reduced 2D and 1D spectra, and a description of the reduction and calibration process. We measure spectroscopic redshifts for 178 of the objects targeted extending up to $z=13.2$. We present a catalog of all emission lines detected at $S/N>5$, and our redshift determinations for the targets. Combined with the first JADES NIRCam data release, these public JADES spectroscopic and imaging datasets provide a new foundation for discoveries of the infrared universe by the worldwide scientific community.

Figures (22)

• Figure 1: Overlay of target shutter positions onto the images, with the illuminated shutter regions outlined ($0\farcs46\times 0\farcs20$). The first 63 targets sorted by NIRSpec ID number (IDs 2333--7762) are shown here, starting at the top left, with the other 190 targets shown in Appendix \ref{['sec:postage_stamps']}. A red outline indicates that the image is derived from the JWST/NIRCam F115W/F150W/F200W images from JADES (blue/green/red channels), and an orange outline denotes HST ACS-F850LP/WFC3-F125W/WFC3-F160W images. The individual images are $1\farcs 0$ on a side, and are centred on the input coordinate of the target. North is up and East is to the left.
• Figure 2: Field layout of the NIRSpec Deep-HST observations presented in this paper. The green rectange is the region covered by the original HST/ACS Hubble Ultra Deep Field. The red rectangle is the smaller area covered in the Ultra Deep HST/WFC 3 imaging. The background image is the NIRCam F200W from JADES, except for the region to the right of the blue line which has not yet been observed by NIRCam; we show in this region the HST/WFC 3 from GOODS-South/CANDELS in blue. The short red lines denote the five-shutter ($\approx 2\farcs 6$) extent observed (three open shutters each target per observation, nodded by $\pm 1$ shutter for background subtraction). The the four quadrants of the NIRSpec MSA are clearly visible. More detailed views of each quadrant with the target ID numbers marked are shown in Figures \ref{['fig:open_shutters']} and Figures \ref{['fig:quad1']}, \ref{['fig:quad2']} & \ref{['fig:quad4']}, which also show the sub-set of targets with grating spectra. The yellow scale bar at the bottom left is 1 arcmin in length.
• Figure 3: One of the four MSA quadrants (Q3), showing allocation of micro-shutters to targets. The other quadrants are shown in Appendix \ref{['sec:MSAquads']}. Those shutters in green are covered by both the grating configurations and the low-dispersion prism. The red shutters are open only in the prism observations, as they would lead to overlapping spectra for our high priority targets in the grating configuration. Three micro-shutters are opened for each target, but the nodding by $\pm 1$ shutter means that spectra are obtained over the areas covered by five shutters (including background) which are displayed. The field displayed is the NIRCam F200W image, and is $1.8$ arcmin on a side. North is up and East is to the left. Shutters with the prefix 'B' are empty sky background.
• Figure 4: Comparison of spectral measurements between the low-dispersion prism and medium-dispersion gratings. Upper: Comparison of redshift as determined from Prism/Clear and $R\approx1000$ grating observations for targets with emission lines clearly detected in both modes. There is a systematic offset of $\Delta z=0.0039$, with the prism yielding systematically higher redshifts. Lower: Comparison of emission lines fluxes measured from prism and $R\approx1000$ grating. Measurements derived from the grating are systematically higher with a median value of $f_{R\approx1000}/f_{\rm PRISM}$ = 1.105 and a standard deviation of 0.298
• Figure 5: Histogram of spectroscopic redshifts obtained from $S/N>5$ emission lines. The separate histograms are for the medium-dispersion $R\approx1000$ gratings (flag A, darkest purple), additional galaxies with $S/N>5$ emission lines detected with the low-dispersion $R\approx30-300$ prism (flag B, lighter purple histogram) and galaxies with more marginal redshifts (flag C, lightest histogram).