The JWST EXCELS survey: direct estimates of C, N, and O abundances in two relatively metal-rich galaxies at $\mathbf{z\simeq5}$
| Autor: | Arellano-Córdova, K. Z., Cullen, F., Carnall, A. C., Scholte, D., Stanton, T. M., Kobayashi, C., Martinez, Z., Berg, D. A., Barrufet, L., Begley, R., Donnan, C. T., Dunlop, J. S., Hamadouche, M. L., McLeod, D. J., McLure, R. J., Rowlands, K., Shapley, A. E. |
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| Rok vydání: | 2024 |
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| Druh dokumentu: | Working Paper |
| Popis: | We present a spectroscopic analysis of two star-forming galaxies at z~5 observed with JWST/NIRSpec as part of the Early eXtragalactic Continuum and Emission Line Science (EXCELS) survey. The detection of the C III]$\lambda\lambda$1906,09, [O II]$\lambda\lambda$3726,29, [O III]$\lambda\lambda$4363,5007, and [N II]$\lambda$6584 nebular emission lines enables investigation of the C/O, N/O, and C/N abundance ratios using the temperature-sensitive method. The two galaxies have stellar masses of log($M_{\star}$/M$_{\odot}$ ) = 8.13$\pm$0.09 and log($M_{\star}$/M$_{\odot}$ )=8.52$\pm$0.13 and corresponding metallicities of Z~0.2Z$_{\odot}$ and Z~0.3Z$_{\odot}$. These metallicities are somewhat higher than is typical for other z>5 galaxies with similar stellar mass and are in fact comparable to high-redshift analogue galaxies at z~0. Both galaxies display evidence for N/O enhancement with respect to the z~0 sample, with log(N/O)=-1.07$\pm$0.17 and log(N/O)=-0.86$\pm$0.15 respectively. In contrast, we find low C abundances, with log(C/O)=-0.82$\pm$0.22 and log(C/O)=-1.02$\pm$0.22, consistent with the predicted yields of core-collapse supernovae. Following the trend observed in other high-redshift sources, we find that the C/N ratios are lower at fixed O/H compared to the majority of local galaxies. In contrast to the top-heavy IMF invoked in some studies to explain low C/N ratios in metal-poor galaxies, we find, via comparison to chemical evolution models, that a standard or bottom-heavy IMF better explains the observed abundance ratios in more enriched systems due to an increase in N-enrichment from intermediate mass (4-7M$_{\odot}$) stars. Our results demonstrate that robust measurements of CNO abundances with JWST can reveal unique enrichment pathways in galaxies as a function of both metallicity and redshift. Comment: 17 pages, 8 Figures, and 3 Tables. Submitted to MNRAS. Comments Welcome |
| Databáze: | arXiv |
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