Direct T _e-based Metallicities of z=2-9 Galaxies with JWST/NIRSpec: Empirical Metallicity Calibrations Applicable from Reionization to Cosmic Noon

We report detections of the [O iii]lambda 4364 auroral emission line for 16 galaxies at z = 2.1-8.7, measured from JWST/NIRSpec observations obtained as part of the Cosmic Evolution Early Release Science (CEERS) survey program. We combine this CEERS sample with 9 objects from the literature at z = 4-9 with auroral-line detections from JWST/NIRSpec and 21 galaxies at z = 1.4-3.7 with auroral-line detections from ground-based spectroscopy. We derive electron temperature (T-e) and direct-method oxygen abundances for the combined sample of 46 star-forming galaxies at z = 1.4-8.7. We use these measurements to construct the first high-redshift empirical T-e-based metallicity calibrations for the strong-line ratios [O iii]/H beta, [O ii]/H beta, R23 = ([O iii]+[O ii])/H beta, [O iii]/[O ii], and [Ne iii]/[O ii]. These new calibrations are valid over 12+log(O/H) = 7.4-8.3 and can be applied to samples of star-forming galaxies at z = 2-9, leading to an improvement in the accuracy of metallicity determinations at Cosmic Noon and in the Epoch of Reionization. The high-redshift strong-line relations are offset from calibrations based on typical z similar to 0 galaxies or H ii regions, reflecting the known evolution of ionization conditions between z similar to 0 and z similar to 2. Deep spectroscopic programs with JWST/NIRSpec promise to improve statistics at the low and high ends of the metallicity range covered by the current sample, as well as to improve the detection rate of [N ii]lambda 6585 and thus allow the future assessment of N-based indicators. These new high-redshift calibrations will enable accurate characterizations of metallicity scaling relations at high redshift, improving our understanding of feedback and baryon cycling in the early Universe.