A Comprehensive Metallicity Analysis of J0332−3557: Establishing a z ∼ 4 Anchor for Direct Gas Metallicity and C/O Abundance Investigations
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jats:titleAbstract</jats:title> jats:pWe provide one of the most comprehensive metallicity studies at jats:italicz</jats:italic> ∼ 4 by analyzing the UV/optical Hubble Space Telescope photometry and rest-frame Very Large Telescope (VLT)/FORS2 UV and VLT/XSHOOTER optical spectra of J0332−3557, a gravitationally lensed galaxy magnified by a factor of 20. With a 5jats:italicσ</jats:italic> detection of the auroral O jats:sciii</jats:sc>] jats:italicλ</jats:italic>1666 line, we are able to derive a direct gas metallicity estimate for our target. We find jats:italicZ</jats:italic> jats:subgas</jats:sub> jats:inline-formula jats:tex-math
</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> mml:mo=</mml:mo> mml:mn12</mml:mn> mml:mo+</mml:mo> mml:milog</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="normal">O</mml:mi> mml:mrow <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo stretchy="false">)</mml:mo> mml:mo=</mml:mo> mml:mn8.26</mml:mn> mml:mo±</mml:mo> mml:mn0.06</mml:mn> </mml:math> </jats:inline-formula>, which is compatible with an increase of both the gas fraction and the outflow metal loading factor from jats:italicz</jats:italic> ∼ 0 to jats:italicz</jats:italic> ∼ 4. J0332−3557 is the most metal-rich individual galaxy at jats:italicz</jats:italic> ∼ 4 for which the C/O ratio has been measured. We derive a low log(C/O) = −1.02 ± 0.2, which suggests that J0332−3557 is in the early stages of interstellar medium carbon enrichment driven mostly by massive stars. The low C/O abundance also indicates that J0332−3557 is characterized by a low star formation efficiency, higher yields of oxygen, and longer burst duration. We find that EWjats:subC jats:scIII</jats:sc>]1906,9</jats:sub> is as low as ∼3 Å, and the main drivers of the low EWjats:subC jats:scIII</jats:sc>]1906,9</jats:sub> are the higher gas metallicity and the low C/O abundance. J0332−3557 is characterized by one diffuse and two more compact regions ∼1 kpc in size. We find that the carbon emission mostly originates in the compact knots. Our study on J0332−3557 serves as an anchor for studies investigating the evolution of metallicity and C/O abundance across different redshifts.</jats:p>
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Acknowledgements: The authors wish to thank the referee for constructive comments that improved the paper substantially. The authors thank Prof. R. Cabanac for providing the J0332 data from the 2008 work. A.C. thanks H. Williams for providing insights on implementing nonparametric SFHs in Prospector. A.C. also thanks Dr. F. Cullen for the SFR results from the NIRVANDELS data, Prof. H. Nakajima for providing the photoionization models describing the evolution of the EWC III]1906,9 as a function of metallicity, and Prof. Max Pettini for helpful conversation and discussion. A.C. and D.K.E. were supported by the US National Science Foundation (NSF) through Astronomy & Astrophysics grant AST-1909198. G.B. was supported by the NSF through grants AST-1615814 and AST-1751404. This work is based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 086.A-0035(A) and 094.A-0252(A). This research is also based in part on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 14093.
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1538-4357
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National Science Foundation (NSF) (AST-1615814)
National Science Foundation (NSF) (AST-1751404)