The Direct-method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High Noon
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Steward Observatory, University of ArizonaIssue Date
2023-05-12
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Institute of PhysicsCitation
Timothy Gburek et al 2023 ApJ 948 108Journal
Astrophysical JournalRights
© 2023. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
We present a Keck/MOSFIRE rest-optical composite spectrum of 16 typical gravitationally lensed star-forming dwarf galaxies at 1.7 ≲ z ≲ 2.6 (z mean = 2.30), all chosen independent of emission-line strength. These galaxies have a median stellar mass of log ( M * / M ⊙ ) med = 8.29 − 0.43 + 0.51 and a median star formation rate of S F R H α m e d = 2.25 − 1.26 + 2.15 M ⊙ y r − 1 . We measure the faint electron-temperature-sensitive [O iii] λ4363 emission line at 2.5σ (4.1σ) significance when considering a bootstrapped (statistical-only) uncertainty spectrum. This yields a direct-method oxygen abundance of 12 + log ( O / H ) direct = 7.88 − 0.22 + 0.25 ( 0.15 − 0.06 + 0.12 Z ⊙ ). We investigate the applicability at high z of locally calibrated oxygen-based strong-line metallicity relations, finding that the local reference calibrations of Bian et al. best reproduce (≲0.12 dex) our composite metallicity at fixed strong-line ratio. At fixed M *, our composite is well represented by the z ∼ 2.3 direct-method stellar mass—gas-phase metallicity relation (MZR) of Sanders et al. When comparing to predicted MZRs from the IllustrisTNG and FIRE simulations, having recalculated our stellar masses with more realistic nonparametric star formation histories ( log ( M * / M ⊙ ) med = 8.92 − 0.22 + 0.31 ) , we find excellent agreement with the FIRE MZR. Our composite is consistent with no metallicity evolution, at fixed M * and SFR, of the locally defined fundamental metallicity relation. We measure the doublet ratio [O ii] λ3729/[O ii] λ3726 = 1.56 ± 0.32 (1.51 ± 0.12) and a corresponding electron density of n e = 1 − 0 + 215 cm − 3 ( n e = 1 − 0 + 74 cm − 3 ) when considering the bootstrapped (statistical-only) error spectrum. This result suggests that lower-mass galaxies have lower densities than higher-mass galaxies at z ∼ 2. © 2023. The Author(s). Published by the American Astronomical Society.Note
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0004-637XVersion
Final Published Versionae974a485f413a2113503eed53cd6c53
10.3847/1538-4357/acb153
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Except where otherwise noted, this item's license is described as © 2023. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.