The JWST EXCELS survey: Probing strong-line diagnostics and the chemical evolution of galaxies over cosmic time using Te-metallicities
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2025
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| author | Scholte, D. Cullen, F. Carnall, A. C. Arellano-Córdova, K. Z. Stanton, T. M. Barrufet, L. Donnan, C. T. Dunlop, J. S. Leung, H. -H. McLeod, D. J. McLure, R. J. Moustakas, J. M. Pollock, C. L. Shapley, A. E. Stevenson, S. Zou, H. |
| author_facet | Scholte, D. Cullen, F. Carnall, A. C. Arellano-Córdova, K. Z. Stanton, T. M. Barrufet, L. Donnan, C. T. Dunlop, J. S. Leung, H. -H. McLeod, D. J. McLure, R. J. Moustakas, J. M. Pollock, C. L. Shapley, A. E. Stevenson, S. Zou, H. |
| contents | We present an analysis of the rest-frame optical spectra of 22 [OIII]$λ$4363 detected galaxies in the redshift range $1.65 < z < 7.92$ (with $\langle z \rangle$ = 4.05) from JWST/NIRSpec medium-resolution observations taken as part of the EXCELS survey. To supplement these high-redshift sources, we also consider a sample of 782 local [OIII]$λ$4363 detected galaxies from the DESI Early Data Release. Our analysis demonstrates that many strong-line calibrations are biased in the early Universe due to the systematic evolution in ionization conditions with redshift. However, the recently introduced $\widehat{R}$ calibration mostly removes the dependence on ionization state and can be considered a largely redshift-independent calibration. In a similar spirit, we introduce a new strong-line diagnostic, $\widehat{RNe}$, which can be used to robustly estimate metallicities when the [OIII]$λ$5007 is redshifted out of the wavelength range of JWST/NIRSpec at $z > 9.5$. We also show that strong-line diagnostics using the [NII]$λ$6584 emission line are likely to be biased at high-redshift due to a moderate enhancement in the average N/O abundance ratios (at fixed O/H) in these sources. Finally, we discuss the location of our new [OIII]$λ$4363 detected galaxies at $z \simeq 4$ on the mass-metallicity plane and investigate the redshift evolution of the fundamental metallicity relation (FMR). We find tentative evidence for an increasing deviation from the FMR at $z > 4$ which might indicate fundamental differences in the baryon cycle at these redshifts. However, more data are required as our high-redshift constraints are still based on a relatively small sample of galaxies and the significance of the deviation is strongly dependent on the assumed form of the fundamental metallicity relation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_10499 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The JWST EXCELS survey: Probing strong-line diagnostics and the chemical evolution of galaxies over cosmic time using Te-metallicities Scholte, D. Cullen, F. Carnall, A. C. Arellano-Córdova, K. Z. Stanton, T. M. Barrufet, L. Donnan, C. T. Dunlop, J. S. Leung, H. -H. McLeod, D. J. McLure, R. J. Moustakas, J. M. Pollock, C. L. Shapley, A. E. Stevenson, S. Zou, H. Astrophysics of Galaxies We present an analysis of the rest-frame optical spectra of 22 [OIII]$λ$4363 detected galaxies in the redshift range $1.65 < z < 7.92$ (with $\langle z \rangle$ = 4.05) from JWST/NIRSpec medium-resolution observations taken as part of the EXCELS survey. To supplement these high-redshift sources, we also consider a sample of 782 local [OIII]$λ$4363 detected galaxies from the DESI Early Data Release. Our analysis demonstrates that many strong-line calibrations are biased in the early Universe due to the systematic evolution in ionization conditions with redshift. However, the recently introduced $\widehat{R}$ calibration mostly removes the dependence on ionization state and can be considered a largely redshift-independent calibration. In a similar spirit, we introduce a new strong-line diagnostic, $\widehat{RNe}$, which can be used to robustly estimate metallicities when the [OIII]$λ$5007 is redshifted out of the wavelength range of JWST/NIRSpec at $z > 9.5$. We also show that strong-line diagnostics using the [NII]$λ$6584 emission line are likely to be biased at high-redshift due to a moderate enhancement in the average N/O abundance ratios (at fixed O/H) in these sources. Finally, we discuss the location of our new [OIII]$λ$4363 detected galaxies at $z \simeq 4$ on the mass-metallicity plane and investigate the redshift evolution of the fundamental metallicity relation (FMR). We find tentative evidence for an increasing deviation from the FMR at $z > 4$ which might indicate fundamental differences in the baryon cycle at these redshifts. However, more data are required as our high-redshift constraints are still based on a relatively small sample of galaxies and the significance of the deviation is strongly dependent on the assumed form of the fundamental metallicity relation. |
| title | The JWST EXCELS survey: Probing strong-line diagnostics and the chemical evolution of galaxies over cosmic time using Te-metallicities |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2502.10499 |