THE MOSDEF SURVEY: DETECTION OF [O III]λ4363 AND THE DIRECT-METHOD OXYGEN ABUNDANCE OF A STAR-FORMING GALAXY AT z = 3.08* ∗ Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.
Published Web Location
https://iopscience.iop.org/article/10.3847/2041-8205/825/2/L23/metaAbstract
We present measurements of the electron-temperature-based oxygen abundance for a highly star-forming galaxy at z = 3.08, COSMOS-1908. This is the highest redshift at which [O iii]λ4363 has been detected and the first time that this line has been measured at z > 2. We estimate an oxygen abundance of 12 + log(O/H) = 8.00-0.14+0.13. This galaxy is a low-mass (109.3 M⊙), highly star-forming (∼50M⊙ yr-1) system that hosts a young stellar population (∼160 Myr). We investigate the physical conditions of the ionized gas in COSMOS-1908 and find that this galaxy has a high ionization parameter, little nebular reddening (E(B-V)gas < 0.14), and a high electron density (ne ∼ 500 cm-3). We compare the ratios of strong oxygen, neon, and hydrogen lines to the direct-method oxygen abundance for COSMOS-1908 and additional star-forming galaxies at z=0-1.8 with [O iii]λ4363 measurements and show that galaxies at z ∼ 1-3 follow the same strong-line correlations as galaxies in the local universe. This agreement suggests that the relationship between ionization parameter and O/H is similar for z∼0 and high-redshift galaxies. These results imply that metallicity calibrations based on lines of oxygen, neon, and hydrogen do not strongly evolve with redshift and can reliably estimate abundances out to Z ∼ 3, paving the way for robust measurements of the evolution of the mass-metallicity relation to high redshift.
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