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Main Authors: Khostovan, Ali Ahmad, Sanders, Ryan L., Shapley, Alice E., Topping, Michael W., Reddy, Naveen A., Garcia, Alex M., Berg, Danielle A., Clarke, Leonardo, Cullen, Fergus, Ellis, Richard S., Schreiber, N. M. Förster, Glazebrook, Karl, Jones, Tucker, McLeod, Derek J., Pahl, Anthony J., Pettini, Max, Torrey, Paul
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2512.16989
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author Khostovan, Ali Ahmad
Sanders, Ryan L.
Shapley, Alice E.
Topping, Michael W.
Reddy, Naveen A.
Garcia, Alex M.
Berg, Danielle A.
Clarke, Leonardo
Cullen, Fergus
Ellis, Richard S.
Schreiber, N. M. Förster
Glazebrook, Karl
Jones, Tucker
McLeod, Derek J.
Pahl, Anthony J.
Pettini, Max
Torrey, Paul
author_facet Khostovan, Ali Ahmad
Sanders, Ryan L.
Shapley, Alice E.
Topping, Michael W.
Reddy, Naveen A.
Garcia, Alex M.
Berg, Danielle A.
Clarke, Leonardo
Cullen, Fergus
Ellis, Richard S.
Schreiber, N. M. Förster
Glazebrook, Karl
Jones, Tucker
McLeod, Derek J.
Pahl, Anthony J.
Pettini, Max
Torrey, Paul
contents We present new constraints on the Mass -- Metallicity (MZR) and Fundamental Metallicity Relations (FMR) using a sample of 34 galaxies at $1.38\leq~z\leq~3.5$ (median $z=2.28$). These galaxies have direct $T_e$ measurements from [O\sc{iii}]4363Å~and/or [O\sc{ii}]7320,7331Å~auroral emission lines detected with \textit{JWST}/NIRSpec as part of the AURORA survey. The detection of both oxygen auroral lines allows for dual-zone direct $T_e$ measurements and expands the dynamic range in $12+\log\mathrm{(O/H)}$ (7.68 to 8.65 dex), stellar mass ($10^{8}$ to $10^{10.4}$ M$_\odot$), and star-formation rate ($1$ to $100$ M$_\odot$ yr$^{-1}$) compared to previous direct $T_e$ studies of the high-redshift MZR and FMR. We characterize the $z\sim2$ MZR and find a slope of $0.27\pm0.04$ and normalization of $12+\log\mathrm{(O/H)} = 8.44\pm0.04$ at $10^{10}$ M$_\odot$ with an intrinsic scatter of 0.10 dex, consistent with past strong-line MZR measurements. Comparisons with $z\sim2$ predictions from six simulations reveal that none reproduce our observed MZR normalization evolution between $z\sim0$ and $z\sim2$. This discrepancy suggests current models do not fully capture the chemical enrichment and feedback processes occurring at cosmic noon. However, all 34 galaxies are on or above the star-forming main sequence such that our sample may be biased towards lower $12+\log\mathrm{(O/H)}$ if the FMR persists at $z\sim2$. Correcting for this selection effect would increase O/H by $\approx0.1$ dex at 10$^{9.3}$ M$_\odot$ (the median mass of our sample) bringing our MZR into better agreement with that of \texttt{TNG}. Lastly, we find our $z\sim2.3$ sample is consistent with the $z\sim0$ FMR within 0.1 dex in O/H, indicating that the smooth secular mechanisms regulating chemical enrichment, star formation, stellar mass, and outflows were in place at cosmic noon.
format Preprint
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institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The AURORA Survey: The Mass -- Metallicity and Fundamental Metallicity Relations at $z \sim 2.3$ Based Purely on Direct $T_e$ Metallicities
Khostovan, Ali Ahmad
Sanders, Ryan L.
Shapley, Alice E.
Topping, Michael W.
Reddy, Naveen A.
Garcia, Alex M.
Berg, Danielle A.
Clarke, Leonardo
Cullen, Fergus
Ellis, Richard S.
Schreiber, N. M. Förster
Glazebrook, Karl
Jones, Tucker
McLeod, Derek J.
Pahl, Anthony J.
Pettini, Max
Torrey, Paul
Astrophysics of Galaxies
We present new constraints on the Mass -- Metallicity (MZR) and Fundamental Metallicity Relations (FMR) using a sample of 34 galaxies at $1.38\leq~z\leq~3.5$ (median $z=2.28$). These galaxies have direct $T_e$ measurements from [O\sc{iii}]4363Å~and/or [O\sc{ii}]7320,7331Å~auroral emission lines detected with \textit{JWST}/NIRSpec as part of the AURORA survey. The detection of both oxygen auroral lines allows for dual-zone direct $T_e$ measurements and expands the dynamic range in $12+\log\mathrm{(O/H)}$ (7.68 to 8.65 dex), stellar mass ($10^{8}$ to $10^{10.4}$ M$_\odot$), and star-formation rate ($1$ to $100$ M$_\odot$ yr$^{-1}$) compared to previous direct $T_e$ studies of the high-redshift MZR and FMR. We characterize the $z\sim2$ MZR and find a slope of $0.27\pm0.04$ and normalization of $12+\log\mathrm{(O/H)} = 8.44\pm0.04$ at $10^{10}$ M$_\odot$ with an intrinsic scatter of 0.10 dex, consistent with past strong-line MZR measurements. Comparisons with $z\sim2$ predictions from six simulations reveal that none reproduce our observed MZR normalization evolution between $z\sim0$ and $z\sim2$. This discrepancy suggests current models do not fully capture the chemical enrichment and feedback processes occurring at cosmic noon. However, all 34 galaxies are on or above the star-forming main sequence such that our sample may be biased towards lower $12+\log\mathrm{(O/H)}$ if the FMR persists at $z\sim2$. Correcting for this selection effect would increase O/H by $\approx0.1$ dex at 10$^{9.3}$ M$_\odot$ (the median mass of our sample) bringing our MZR into better agreement with that of \texttt{TNG}. Lastly, we find our $z\sim2.3$ sample is consistent with the $z\sim0$ FMR within 0.1 dex in O/H, indicating that the smooth secular mechanisms regulating chemical enrichment, star formation, stellar mass, and outflows were in place at cosmic noon.
title The AURORA Survey: The Mass -- Metallicity and Fundamental Metallicity Relations at $z \sim 2.3$ Based Purely on Direct $T_e$ Metallicities
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2512.16989