Galaxy Size Reveals Connection Between Gas Inflow History and Metallicity
A new study using MaNGA integral field spectroscopy finds that galaxy size is a key predictor of gas metallicity, reflecting differences in long-term gas inflow histories rather than short-term fluctuations. Researchers analyzed ~1,500 star-forming galaxies, finding that inner gas mass is the most important parameter after stellar mass in predicting chemical abundances. The results challenge existing explanations for the mass-metallicity relation and suggest galaxy size encodes the full chain from halo assembly to current gas reservoirs and metallicity.
Researchers have submitted a study to Monthly Notices of the Royal Astronomical Society arguing that galaxy size encodes the link between halo assembly histories, long-term gas inflow histories, and gas-phase metallicity. Using MaNGA integral field spectroscopy combined with HI-MaNGA gas masses and MaNGA DynPop dynamical masses, the team analyzed approximately 1,500 star-forming galaxies. They find that inner gas mass is the single most important predictor of gas metallicity after stellar mass, outperforming star-formation rate and optical size individually. Crucially, the strong correlation between inner gas mass and galaxy size rules out short-term inflow fluctuations as the driver of mass-metallicity relation residuals. The study also challenges the hypothesis that deeper gravitational potentials in compact galaxies confer higher metallicities, showing instead that compact galaxies have lower dynamical masses. Chemical evolution modeling supports the interpretation that compact galaxies experienced earlier inflow histories, leading to more rapidly declining gas reservoirs and consequently higher metallicities at late times. The findings are corroborated by equivalent results for stellar metallicities and gaseous nitrogen-to-oxygen ratios, suggesting the connection reflects genuine long-term chemical evolution.
What's missing
The paper is currently a preprint resubmitted after moderate revisions and has not yet completed peer review, so findings remain provisional. The study relies on optical size as a proxy and is limited to star-forming galaxies in the MaNGA survey footprint, which may not be fully representative of the broader galaxy population.
What different sources said
- arXiv astro-phCenter
Beyond the Fundamental Metallicity Relation: galaxy sizes encode the link between inflow and metallicity
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