JADES Dark Horse: demonstrating high-multiplex observations with JWST/NIRSpec dense-shutter spectroscopy in the JADES Origins Field

Abstract We present JWST/NIRSpec dense-shutter spectroscopy (DSS). This novel observing strategy with the NIRSpec/MSA deliberately permits a high number of controlled spectral overlaps to reach extreme multiplex while retaining the low background of slit spectroscopy. In a single configuration over the JADES Origins Field, we opened shutters on all faint (mF444W < 30 mag) zphot > 3 candidates, prioritising emission-line science and rejecting only bright continuum sources. Using 33.6 and 35.8 ks on-source in G235M and G395M, we observed a single mask with ∼850 sources, obtaining spectroscopic redshifts for ∼540 galaxies over 2.5 ≲ z ≲ 8.9. The per-configuration target density in DSS mode is 4–5× higher than standard no- and low-overlap MSA strategies (<200 sources), with no loss in redshift precision or accuracy. Line-flux sensitivities are 30 percent lower at fixed exposure time, matching the expected increase in background noise, but the gain in survey speed is 5× in our setup, more than justifying the penalty. The measured line sensitivity exceeds NIRCam/WFSS by at least ∼5 × (~25 × in exposure time) at λ ∼ 4 μm, demonstrating that DSS is a compelling method to gain deep, wide-band spectra for large samples. Crucially, NIRSpec/MSA could deliver even higher target allocation densities than those used here. We derive H α-based SFRs, gas-phase metallicities (including a large sample suitable for strong-line calibrations), and identify rare mini-quenched galaxies and broad-line AGN. DSS is immediately applicable wherever deep imaging enables robust pre-selection and astrometry, providing an efficient method to obtain large samples of faint emission-line galaxies, a compelling middle ground between the completeness of slitless surveys and the sensitivity and bandwidth of NIRSpec/MSA.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2026-04-30
DOI
https://doi.org/10.1093/mnras/stag824
Primary Topic
Galaxies: Formation, Evolution, Phenomena
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article
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article

JADES Dark Horse: demonstrating high-multiplex observations with JWST/NIRSpec dense-shutter spectroscopy in the JADES Origins Field

Joris Witstok, Jakob M. Helton, Tobias J. Looser, William Baker et al.
Monthly Notices of the Royal Astronomical Society
Galaxies: Formation, Evolution, Phenomena
article

JADES Dark Horse: demonstrating high-multiplex observations with JWST/NIRSpec dense-shutter spectroscopy in the JADES Origins Field

Joris Witstok, Jakob M. Helton, Tobias J. Looser, William Baker, Eleonora Parlanti, Zihao Wu, Santiago Arribas, I Juodžbalis, J Scholtz, R Maiolino, Xihan Ji, Stefano Carniani, Yongda Zhu, Brant Robertson, Francesco D’Eugenio, Emma Curtis-Lake, Christina C Williams, Dávid Puskás, Benjamin D Johnson, Andrew J Bunker, Gareth C Jones, Hannah Übler, Giacomo Venturi, Charlotte Simmonds, Chris Willott, Alex J Cameron, Jianwei Lyu, Zhiyuan Ji, Michele Perna, Stéphane Charlot, Pierluigi Rinaldi, Fengwu Sun, Sandro Tacchella, Yang Sun, Nimisha Kumari, Kevin Hainline, Jacopo Chevallard, Daniel J Eisenstein, Yuki Isobe, Erica J Nelson, Christopher N A Willmer, Mirko Curti, A Lola Danhaive
article en

Abstract

Abstract We present JWST/NIRSpec dense-shutter spectroscopy (DSS). This novel observing strategy with the NIRSpec/MSA deliberately permits a high number of controlled spectral overlaps to reach extreme multiplex while retaining the low background of slit spectroscopy. In a single configuration over the JADES Origins Field, we opened shutters on all faint (mF444W < 30 mag) zphot > 3 candidates, prioritising emission-line science and rejecting only bright continuum sources. Using 33.6 and 35.8 ks on-source in G235M and G395M, we observed a single mask with ∼850 sources, obtaining spectroscopic redshifts for ∼540 galaxies over 2.5 ≲ z ≲ 8.9. The per-configuration target density in DSS mode is 4–5× higher than standard no- and low-overlap MSA strategies (<200 sources), with no loss in redshift precision or accuracy. Line-flux sensitivities are 30 percent lower at fixed exposure time, matching the expected increase in background noise, but the gain in survey speed is 5× in our setup, more than justifying the penalty. The measured line sensitivity exceeds NIRCam/WFSS by at least ∼5 × (~25 × in exposure time) at λ ∼ 4 μm, demonstrating that DSS is a compelling method to gain deep, wide-band spectra for large samples. Crucially, NIRSpec/MSA could deliver even higher target allocation densities than those used here. We derive H α-based SFRs, gas-phase metallicities (including a large sample suitable for strong-line calibrations), and identify rare mini-quenched galaxies and broad-line AGN. DSS is immediately applicable wherever deep imaging enables robust pre-selection and astrometry, providing an efficient method to obtain large samples of faint emission-line galaxies, a compelling middle ground between the completeness of slitless surveys and the sensitivity and bandwidth of NIRSpec/MSA.

Monthly Notices of the Royal Astronomical Society
Herzberg Institute of Astrophysics (CA), University of Copenhagen (DK), Space Telescope Science Institute (US), Planetary Science Institute (US), Pennsylvania State University (US), European Southern Observatory (DE), Joint Institute for Laboratory Astrophysics (US), University of Arizona (US), University of Hertfordshire (GB), Scuola Normale Superiore (IT), Pontificia Universidad Católica de Chile (CL), University of California, Santa Cruz (US), University of Cambridge (GB), Institut d'Astrophysique de Paris (FR), University of Oxford (GB), Max Planck Institute for Extraterrestrial Physics (DE), DAWN Center for Independent Living (US), Center for Astrophysics Harvard & Smithsonian (US), Centro de Astrobiología (ES), NSF NOIRLab (US), University College London (GB)
Openalex Percentile: Top 7%
Galaxies: Formation, Evolution, Phenomena
DOIOpen Access PDFOpenAlex
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