JWST EXCELS

The EXtragalactic Continuum and Emission Line Science survey is a JWST Cycle 2 spectroscopic program (ID: 3543, PI: A. C. Carnall, F. Cullen) targeted ~350 star-forming and quiescent galaxies with the JWST/NIRSpec medium resolution gratings, with the aim of obtaining deep spectra. Science goals included the formation and quenching mechanisms of quiescent galaxies, and the nebular, chemical, and ionizing properties of star-forming galaxies.

Click the figure below to be redirected to the survey paper (Carnall et al. 2024)

Figure 1. An example star-forming galaxy at z = 5.2 from the EXCELS sample. An emission-line model is shown over the spectral data. Figure taken from Stanton et al. 2026.

Multi-Elemental Abundance Patterns in EXCELS

In Stanton et al. (2025) I derived multi-elemental chemical abundance patterns using the oxygen, neon and argon abundances of eight star-forming galaxies at 1 \leq z \leq 5, finding that high-z galaxies show Ne/O ratios fully consistent with local samples, while they are deficient in Ar with respect to O. These results validate the predictions of chemical evolution modelling, and provided one of the first statistically sized samples showing that Ar can be used as an indirect tracer of \alpha-enhancement.

Figure 2. *Left*: the Ar/O abundance as a function of the argon abundance for the EXCELS galaxies, literature samples, and the predictions of chemical evolution models. *Right*: the weighted average EXCELS abundance compared to planetary nebulae data from Andromeda. Figure taken from Stanton et al. 2025.

Gas-phase metallicity evolution over *2\leq z \leq 8<*

In Stanton et al. (2026) I derived multi-elemental chemical abundance patterns using the oxygen, neon and argon abundances of eight star-forming galaxies at 1 \leq z \leq 5, finding that high-z galaxies show Ne/O ratios fully consistent with local samples, while they are deficient in Ar with respect to O. These results validate the predictions of chemical evolution modelling, and provided one of the first statistically sized samples showing that Ar can be used as an indirect tracer of \alpha-enhancement.

Figure 3. Deviations from the local FMR in EXCELS and literature galaxies as a function of redshift for strong-line calibrationed metallicities (*left*), direct-method metallicities (*centre*), with comparison to simulations (*right*). Figure taken from Stanton et al. 2026.