The JWST EXCELS survey

Authors

• Ho Hin Leung, University of EdinburghFollow
• Adam C. Carnall, University of Edinburgh
• Elizabeth Taylor, University of Edinburgh
• Struan D. Stevenson, University of Edinburgh
• Aliza G. Beverage, University of California Berkeley
• Fergus Cullen, University of Edinburgh
• James S. Dunlop, University of Edinburgh
• Derek J. McLeod, University of Edinburgh
• Ross J. McLure, University of Edinburgh
• Ryan Begley, Armagh Observatory
• Omar Almaini, University of Nottingham
• Stella Antonogiannaki, University of Edinburgh
• Karla Z. Arellano-Córdova, University of Edinburgh
• Laia Barrufet, University of Edinburgh
• Cecilia Bondestam, University of Edinburgh
• Callum T. Donnan, NSF's National Optical-Infrared Astronomy Research Laboratory
• Isaac J.B. Holst, University of Edinburgh
• Feng Yuan F. Liu, University of Edinburgh
• Kate Rowlands, Johns Hopkins University
• Ryan L. Sanders, University of KentuckyFollow
• Dirk Scholte, University of Edinburgh
• Maya Skarbinski, Johns Hopkins University
• Thomas M. Stanton, University of Edinburgh
• Vivienne Wild, University of St Andrews

Abstract

We present deep, medium-resolution (Formula presented) m JWST/NIRSpec spectroscopy for 14 quiescent galaxies at (Formula presented) with (Formula presented), obtained as part of the EXCELS survey. We perform a complete re-reduction of these data, including a custom optimal-extraction approach to combat the spectral ‘wiggles’ that result from undersampling of the NIRSpec spatial PSF. We constrain the star-formation histories and stellar metallicities of these objects via full-spectral fitting, finding a clear stellar age versus stellar mass correlation, in which more massive galaxies assembled their stellar mass at earlier times. This confirms spectroscopically that the archaeological ‘downsizing’ trend was already in place by (Formula presented). The slope of our measured relation ((Formula presented) Gyr per dex in stellar mass) is consistent with literature results at (Formula presented). We do not observe objects with (Formula presented) and ages of more than a few hundred Myr at this epoch, suggesting that recently reported examples of higher-redshift quiescent galaxies at these masses are likely to soon rejuvenate. We measure relatively high stellar metallicities for the majority of our sample, consistent with similar objects at (Formula presented). Finally, we explore evidence for (Formula presented) -enhancement in six older and more luminous galaxies within our sample, finding considerable disagreements in the chemical abundances measured using different stellar population models, different fitted rest-frame wavelength ranges, star-formation history models and fitting codes. We therefore conclude that inferring detailed stellar chemical abundances for the earliest quiescent galaxies remains challenging, and higher signal-to-noise spectra are required (observed frame SNR per resolution element (Formula presented) for (Formula presented)).

Document Type

Article

Publication Date

6-1-2026

Notes/Citation Information

Publisher Copyright: © The Author(s) 2026. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

Digital Object Identifier (DOI)

10.1093/mnras/stag827

Archival?

Archival

Repository Citation

Leung, Ho Hin; Carnall, Adam C.; Taylor, Elizabeth; Stevenson, Struan D.; Beverage, Aliza G.; Cullen, Fergus; Dunlop, James S.; McLeod, Derek J.; McLure, Ross J.; Begley, Ryan; Almaini, Omar; Antonogiannaki, Stella; Arellano-Córdova, Karla Z.; Barrufet, Laia; Bondestam, Cecilia; Donnan, Callum T.; Holst, Isaac J.B.; Liu, Feng Yuan F.; Rowlands, Kate; Sanders, Ryan L.; Scholte, Dirk; Skarbinski, Maya; Stanton, Thomas M.; and Wild, Vivienne, "The JWST EXCELS survey" (2026). Physics and Astronomy Faculty Publications. 775.
https://uknowledge.uky.edu/physastron_facpub/775