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arXiv · 2609.20921

ALMA Chemical Evolution (ACE) survey: The gas fundamental metallicity relation at cosmic noon

I. Langan·I. Shivaei·G. Popping·L. A. Boogaard·N. N. Geesink·M. Kaasinen·A. Pope·R. Popescu·M. Solimano·L. Arriscado·D. Narayanan·M. Parente·N. Reddy·R. L. Sanders
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Abstract

Chemical enrichment shapes how galaxies form and evolve. The gas-phase metallicity is directly linked to the stellar mass, star formation rate, and cold gas of the interstellar medium. Thus, the cold gas fundamental metallicity relation (GFMR) is a powerful tool for probing galaxy evolution, bridging large-scale gas flows modulating the cold gas reservoir and small-scale metal enrichment tracing the cumulative impact of star formation. Constraining all these properties for the same representative sample of galaxies remains challenging yet essential. Using CO(3--2) band 3 observations from the Atacama Large Millimeter/submillimeter Array Chemical Evolution (ACE) survey, we investigated the GFMR in a sample of 26 main-sequence (log(M_*, med)=9.96), subsolar-metallicity (12+log(O/H)_med=8.44) star-forming galaxies (SFGs) at z~2. With 17/26 CO detections, including some of the lowest-metallicity CO detections at cosmic noon, we find that the stellar mass remains the primary driver of the chemical evolution in our sample (sigmaMZR~0.10). Whereas the molecular gas likely plays a secondary role (sigmaGFMR~0.11) similar to that of the star formation rate (sigmaFMR~0.13). This likely reflects our sensitivity to only the CO-bright component of the molecular reservoir. Our results remain consistent with gas-regulator models and suggest the existence of efficient molecular outflows, with an average mass loading factor of eta~4, regulating star formation and chemical enrichment.

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I. Langan, I. Shivaei, G. Popping, L. A. Boogaard, N. N. Geesink, M. Kaasinen, A. Pope, R. Popescu, M. Solimano, L. Arriscado, D. Narayanan, M. Parente, N. Reddy, R. L. Sanders. 2026-09-17. ALMA Chemical Evolution (ACE) survey: The gas fundamental metallicity relation at cosmic noon. https://arxiv.org/abs/2609.20921

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