Abstract
We analyze the rest-optical emission-line ratios of star-forming galaxies at 2.7 ≤ z < 6.5 drawn from the Cosmic Evolution Early Release Science (CEERS) Survey and their relationships with stellar mass (M *). Our analysis includes both line ratios based on the [N ii] λ6583 feature ([N ii] λ6583/Hα, ([O iii] λ5007/Hβ)/([N ii] λ6583/Hα) (O3N2), and [N ii] λ6583/[O ii] λ3727) and those featuring α-elements ([O iii] λ5007/Hβ, [O iii] λ5007/[O ii] λ3727 (O32), ([O iii] λλ4959, 5007 + [O ii] λ3727)/Hβ (R23), and [Ne iii] λ3869/[O ii] λ3727). Given the typical flux levels of [N ii] λ6583 and [Ne iii] λ3869, which are undetected in the majority of individual CEERS galaxies at 2.7 ≤ z < 6.5, we construct composite spectra in bins of M * and redshift. Using these composite spectra, we compare the relationships between emission-line ratios and M * at 2.7 ≤ z < 6.5 with those observed at lower redshift. While there is significant evolution toward higher excitation (e.g., higher [O iii] λ5007/Hβ, O32, O3N2) and weaker nitrogen emission (e.g., lower [N ii] λ6583/Hα and [N ii] λ6583/[O ii] λ3727) between z ∼ 0 and z ∼ 3, we find in most cases that there is no significant evolution in the relationship between line ratio and M * beyond z ∼ 3. The [Ne iii] λ3869/[O ii] λ3727 ratio is anomalous in showing evidence for significant elevation at 4.0 ≤ z < 6.5 at fixed mass, relative to z ∼ 3.3. Collectively, however, our empirical results suggest no significant evolution in the mass-metallicity relationship at 2.7 ≤ z < 6.5. Representative galaxy samples and metallicity calibrations based on existing and upcoming JWST/NIRSpec observations will be required to translate these empirical scaling relations into ones tracing chemical enrichment and gas cycling and to distinguish among descriptions of feedback in galaxy formation simulations at z > 3.
Document Type
Article
Publication Date
2023
Digital Object Identifier (DOI)
https://doi.org/10.3847/2041-8213/acd939
Funding Information
We acknowledge the entire CEERS team for their effort to design and execute this Early Release Science observational program, especially the work to design the MSA observations. This work is based on observations made with the NASA/ ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-03127 for JWST. The specific observations analyzed can be accessed via doi:10.17909/z7p0- 8481. We also acknowledge support from NASA grant JWST- GO-01914. Support for this work was also provided through the NASA Hubble Fellowship grant #HST-HF2-51469.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.
Repository Citation
Shapley, Alice E.; Reddy, Naveen; Sanders, Ryan L.; Topping, Michael W.; and Brammer, Gabriel B., "JWST/NIRSpec Measurements of the Relationships between Nebular Emission-line Ratios and Stellar Mass at z ∼ 3–6" (2023). Physics and Astronomy Faculty Publications. 699.
https://uknowledge.uky.edu/physastron_facpub/699
Notes/Citation Information
© 2023. The Author(s). Published by the American Astronomical Society.
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