The Detection of [O iii] λ4363 in a Lensed, Dwarf Galaxy at z = 2.59: Testing Metallicity Indicators and Scaling Relations at High Redshift and Low Mass
Freeman, William R.
Stark, Daniel P.
AffiliationUniv Arizona, Dept Astron, Steward Observ
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationTimothy Gburek et al 2019 ApJ 887 168
RightsCopyright © 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis 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 email@example.com.
AbstractWe present Keck/MOSFIRE (Multi-Object Spectrometer for InfraRed Exploration) and Keck/LRIS (Low Resolution Imaging Spectrometer) spectroscopy of A1689-217, a lensed (magnification similar to 7.9), star-forming (SFR similar to 16 M-circle dot yr(-1)), dwarf (log(M*/M-circle dot) = 8.07-8.59) Ly alpha emitter (EW0 similar to 138 angstrom) at z = 2.5918. Dwarf galaxies similar to A1689-217 are common at high redshift and likely responsible for reionization, yet few have been studied with detailed spectroscopy. We report a 4.2 sigma detection of the electron-temperature-sensitive [O III] lambda 4363 emission line and use this line to directly measure an oxygen abundance of 12 + log(O/H).=.8.06.+/-.0.12 (similar to 1/4 Z(circle dot)). A1689-217 is the lowest-mass galaxy at z > 2 with an [O III] lambda 4363 detection. Using the rest-optical emission lines, we measure A1689-217's other nebular conditions, including electron temperature (T-e([O III]) similar to 14,000 K), electron density (n(e) similar to 220 cm(-3)), and reddening (E(B-V) similar to 0.39). We study relations between strong-line ratios and direct metallicities with A1689-217 and other galaxies with [O III].4363 detections at z similar to 0-3.1, showing that the locally calibrated, oxygen-based, strong-line relations are consistent from z similar to 0 to 3.1. We also show additional evidence that the O-32 versus R-23 excitation diagram can be utilized as a redshift-invariant, direct-metallicity-based, oxygen abundance diagnostic out to z similar to 3.1. From this excitation diagram and the strong-line ratio-metallicity plots, we observe that the ionization parameter at fixed O/H is consistent with no redshift evolution. Although A1689-217 is metal-rich for its M* and star formation rate, we find it to be consistent within the large scatter of the low-mass end of the fundamental metallicity relation.
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