Episodic Star Formation - II. The Origin of the Fundamental Metallicity Relation
Abstract
The Fundamental Metallicity Relation (FMR) extends the mass-metallicity relation (MZR) by including star formation rate (SFR) as a third parameter. At fixed stellar mass, galaxies with higher SFRs tend to have lower gas-phase metallicities. We investigate the physical origin of the FMR in the context of episodic star formation (Gui et al. 2026, paper I of this series) by tracing the evolution histories of 8,979 central star-forming galaxies selected at z=0 in TNG100 back to z=1. We find that the overall MZR scatter at z=0 (∼0.11 dex) comprises both long-lived differences among galaxies (∼0.09 dex) and temporal fluctuations within individual galaxies (∼ 0.07 dex). The galaxy-to-galaxy component shows an anticorrelation between SFR and gas-phase metallicity, as shown by the observed FMR. As for the consequence from temporal fluctuation, we track individual histories and stack the upward and downward SFR phases of a refined sample. Time-shift analysis and stacked histories show a well-behaved sequence in which the cold non-star-forming gas reservoir increases (decreases) first, followed by a decrease (increase) in gas-phase metallicity and then a rise (decline) in SFR. This ordering is consistent with a physical scenario where metal-poor gas first replenishes the cold reservoir and dilutes the gas before SFR rises to the peak, followed by feedback-driven gas heating/removal, resulting in a shift in metallicity from dilution to enrichment as SFR decreases towards the valley. This naturally explains the anticorrelation between the SFR and gas-phase metallicities as indicated by the observed FMR.
Related
- ALMA Chemical Evolution (ACE) survey: The gas fundamental metallicity relation at cosmic noon
- Galaxies Below the Fundamental Metallicity Relation Are Morphologically Disturbed: Merian Hα Morphologies and DESI Metallicities
- The Role of Star Formation and Morphology in the Mass-Metallicity Relation of Galaxies at Cosmic Noon
- Cluster Ages to Reconstruct the Milky Way Assembly (CARMA). VI. The age-metallicity relation of in situ clusters and the age of the Universe
- The JADES Mass–Metallicity and Fundamental Metallicity Relations at z ≳ 2 Using New High-redshift Metallicity Calibrations
BibTeX
@misc{mei2026episodic,
title = {{Episodic Star Formation - II. The Origin of the Fundamental Metallicity Relation}},
author = {Xuelun Mei and Dandan Xu and Cheng Li and Yuqian Gui and Haoyi Wang},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.03645},
eprint = {2611.03645},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.03645},
}
RIS
TY - UNPB
TI - Episodic Star Formation - II. The Origin of the Fundamental Metallicity Relation
AU - Xuelun Mei
AU - Dandan Xu
AU - Cheng Li
AU - Yuqian Gui
AU - Haoyi Wang
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.03645
UR - https://arxiv.org/abs/2611.03645
AB - The Fundamental Metallicity Relation (FMR) extends the mass-metallicity relation (MZR) by including star formation rate (SFR) as a third parameter. At fixed stellar mass, galaxies with higher SFRs tend to have lower gas-phase metallicities. We investigate the physical origin of the FMR in the context of episodic star formation (Gui et al. 2026, paper I of this series) by tracing the evolution histories of 8,979 central star-forming galaxies selected at z=0 in TNG100 back to z=1. We find that the overall MZR scatter at z=0 (∼0.11 dex) comprises both long-lived differences among galaxies (∼0.09 dex) and temporal fluctuations within individual galaxies (∼ 0.07 dex). The galaxy-to-galaxy component shows an anticorrelation between SFR and gas-phase metallicity, as shown by the observed FMR. As for the consequence from temporal fluctuation, we track individual histories and stack the upward and downward SFR phases of a refined sample. Time-shift analysis and stacked histories show a well-behaved sequence in which the cold non-star-forming gas reservoir increases (decreases) first, followed by a decrease (increase) in gas-phase metallicity and then a rise (decline) in SFR. This ordering is consistent with a physical scenario where metal-poor gas first replenishes the cold reservoir and dilutes the gas before SFR rises to the peak, followed by feedback-driven gas heating/removal, resulting in a shift in metallicity from dilution to enrichment as SFR decreases towards the valley. This naturally explains the anticorrelation between the SFR and gas-phase metallicities as indicated by the observed FMR.
ER -