On the importance of medium-resolution continuum spectroscopy for JWST's extragalactic legacy
Abstract
We argue for a significant investment of JWST time into an extremely deep medium-resolution NIRSpec MSA survey targeting a large, representative sample of high-redshift (z>1.5) galaxies, specifically intended to obtain high-SNR continuum detections. This is only possible with JWST, and no planned future instrumentation has similar capabilities, meaning that obtaining such observations with JWST must be urgently prioritised. The vast majority of existing archival NIRSpec observations are not deep enough for continuum science, being focused on the detection of emission lines. Deeper continuum data opens up the ability to constrain a much wider range of key galaxy physical parameters, including stellar population ages and metallicities, stellar kinematics and neutral gas physical properties, inflows and outflows. Such measurements will provide crucial insight into quenching physics, galaxy dynamical masses, merger histories, pristine early star-formation, reionization and the physics of Little Red Dots, as well as enabling all of the emission-line science that can be achieved with shallower observations. To facilitate future survey planning, we present an empirically derived relationship between rest-optical continuum SNR in JWST NIRSpec medium-resolution data, rest-optical apparent magnitude and exposure time, which we show to be independent of redshift (and hence the grating used). We then provide a 1000-hour sketch survey plan based on achieving the continuum SNR =20/pixel necessary to constrain key physical properties and scaling relations for a large galaxy sample at z>1.5. We finally discuss NIRSpec sky subtraction strategies, which are of critical importance for continuum SNR.
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BibTeX
@misc{carnall2026importance,
title = {{On the importance of medium-resolution continuum spectroscopy for JWST's extragalactic legacy}},
author = {Adam C. Carnall and Ho-Hin Leung and Struan D. Stevenson and Elizabeth Taylor and Abdurro'uf and Stella Antonogiannaki and Karla Z. Arellano-Cordova and William M. Baker and Guillermo Barro and Arghyadeep Basu and Ryan Begley and Sirio Belli and Danielle A. Berg and Aliza G. Beverage and Rachel Bezanson and Souradeep Bhattacharya and Cecilia Bondestam and Andrew J. Bunker and Emilie Burnham and Alex J. Cameron and Chloe M. Cheng and Yingjie Cheng and M. C. Cooper and Isa G. Cox and Fergus Cullen and Emma Curtis-Lake and Romeel Dave and Rebecca L. Davies and Miroslava Dessauges-Zavadsky and Mark Dickinson and Callum T. Donnan and Qiao Duan and Kenneth J. Duncan and James S. Dunlop and Andreas L. Faisst and Steven L. Finkelstein and Sophia Flury and Anna R. Gallazzi and Adriana Gargiulo and Steven Gillman and Karl Glazebrook and Ansh R. Gupta and Nimish P. Hathi and Kasper E. Heintz and Isaac J. B. Holst and Kei Ito and Christian Kragh Jespersen and Jeyhan S. Kartaltepe and Anton M. Koekemoer and Mariska Kriek and Danial Langeroodi and Joel Leja and Yongming Liang and Yuankang Liu and Derek J. McLeod and Ross McLure and Yurina Nakazato and Themiya Nanayakkara and Gael Noirot and Katherine Ormerod},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.07070},
eprint = {2611.07070},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.07070},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - On the importance of medium-resolution continuum spectroscopy for JWST's extragalactic legacy
AU - Adam C. Carnall
AU - Ho-Hin Leung
AU - Struan D. Stevenson
AU - Elizabeth Taylor
AU - Abdurro'uf
AU - Stella Antonogiannaki
AU - Karla Z. Arellano-Cordova
AU - William M. Baker
AU - Guillermo Barro
AU - Arghyadeep Basu
AU - Ryan Begley
AU - Sirio Belli
AU - Danielle A. Berg
AU - Aliza G. Beverage
AU - Rachel Bezanson
AU - Souradeep Bhattacharya
AU - Cecilia Bondestam
AU - Andrew J. Bunker
AU - Emilie Burnham
AU - Alex J. Cameron
AU - Chloe M. Cheng
AU - Yingjie Cheng
AU - M. C. Cooper
AU - Isa G. Cox
AU - Fergus Cullen
AU - Emma Curtis-Lake
AU - Romeel Dave
AU - Rebecca L. Davies
AU - Miroslava Dessauges-Zavadsky
AU - Mark Dickinson
AU - Callum T. Donnan
AU - Qiao Duan
AU - Kenneth J. Duncan
AU - James S. Dunlop
AU - Andreas L. Faisst
AU - Steven L. Finkelstein
AU - Sophia Flury
AU - Anna R. Gallazzi
AU - Adriana Gargiulo
AU - Steven Gillman
AU - Karl Glazebrook
AU - Ansh R. Gupta
AU - Nimish P. Hathi
AU - Kasper E. Heintz
AU - Isaac J. B. Holst
AU - Kei Ito
AU - Christian Kragh Jespersen
AU - Jeyhan S. Kartaltepe
AU - Anton M. Koekemoer
AU - Mariska Kriek
AU - Danial Langeroodi
AU - Joel Leja
AU - Yongming Liang
AU - Yuankang Liu
AU - Derek J. McLeod
AU - Ross McLure
AU - Yurina Nakazato
AU - Themiya Nanayakkara
AU - Gael Noirot
AU - Katherine Ormerod
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2611.07070
UR - https://arxiv.org/abs/2611.07070
AB - We argue for a significant investment of JWST time into an extremely deep medium-resolution NIRSpec MSA survey targeting a large, representative sample of high-redshift (z>1.5) galaxies, specifically intended to obtain high-SNR continuum detections. This is only possible with JWST, and no planned future instrumentation has similar capabilities, meaning that obtaining such observations with JWST must be urgently prioritised. The vast majority of existing archival NIRSpec observations are not deep enough for continuum science, being focused on the detection of emission lines. Deeper continuum data opens up the ability to constrain a much wider range of key galaxy physical parameters, including stellar population ages and metallicities, stellar kinematics and neutral gas physical properties, inflows and outflows. Such measurements will provide crucial insight into quenching physics, galaxy dynamical masses, merger histories, pristine early star-formation, reionization and the physics of Little Red Dots, as well as enabling all of the emission-line science that can be achieved with shallower observations. To facilitate future survey planning, we present an empirically derived relationship between rest-optical continuum SNR in JWST NIRSpec medium-resolution data, rest-optical apparent magnitude and exposure time, which we show to be independent of redshift (and hence the grating used). We then provide a 1000-hour sketch survey plan based on achieving the continuum SNR =20/pixel necessary to constrain key physical properties and scaling relations for a large galaxy sample at z>1.5. We finally discuss NIRSpec sky subtraction strategies, which are of critical importance for continuum SNR.
ER -