Galaxies Below the Fundamental Metallicity Relation Are Morphologically Disturbed: Merian H$α$ Morphologies and DESI Metallicities

Year: 2026

Type: preprint

Abstract: Empirical results have revealed a connection between a galaxy's metallicity, mass, and star formation rate, known as the fundamental metallicity relation (FMR), in which metallicity increases with stellar mass and decreases with SFR. Physical interpretations of the FMR suggest that actively star-forming galaxies are fueled by pristine gas, likely obtained via IGM accretion or minor mergers. Here we demonstrate the value of galaxy morphology as an additional axis in the FMR. Using medium-band imaging from the Merian Survey, we construct spatially resolved maps of stellar continuum and H$α$ emission for a large sample of galaxies with DESI DR1 spectra, reaching stellar masses down to $10^8$ M$_\odot$. We measure non-parametric morphological parameters from the emission maps and derive gas-phase oxygen abundances from the spectra using strong-line calibrations. We fit a series of simple linear models to explore correlations among the metallicity, stellar mass, sSFR, and morphological parameters. We find that galaxies that are more metal-poor than predicted by the FMR appear particularly disturbed. At fixed stellar mass and sSFR, metallicity is inversely correlated with the asymmetry of both the continuum and H$α$ morphology. The observed trends -- and the existence of particularly metal-poor, morphologically disturbed, highly star-forming galaxies -- are consistent with external burst triggering. Our results indicate that a galaxy's morphology is linked to its metallicity and star formation history, providing an additional observational probe of the physical drivers of elevated star-formation in low-mass galaxies.

Source: arXiv (Cornell University)

DOI: 10.48550/arxiv.2609.26887

Authors: Mintz, Abby, Greene, Jenny E., Danieli, Shany, Kado-Fong, Erin, Leauthaud, Alexie, Li, Jiaxuan, Luo, Yifei, Peter, Annika H. G., Bhattacharyya, Joy, Li, Mingyu, Cruz, Akaxia

Institutions: Princeton University, Tel Aviv University, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, University of California, Santa Cruz, Lawrence Berkeley National Laboratory, Tsinghua University

Language: English

Topic: Galaxies: Formation, Evolution, Phenomena

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, U.S. Department of Energy, Gordon and Betty Moore Foundation, Princeton University, University of Pennsylvania, Ohio State University, University of Portsmouth, University College London, University of Sussex, Deutsche Forschungsgemeinschaft, Ministry of Education, Culture, Sports, Science and Technology, Academia Sinica, Cabinet Office, Government of Japan, Ministério da Ciência, Tecnologia e Inovação, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Financiadora de Estudos e Projetos, Ministerio de Ciencia e Innovación, National Astronomical Observatory of Japan, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, High Energy Accelerator Research Organization, Institut de Física d'Altes Energies, Toray Science Foundation, University of Illinois at Urbana-Champaign, Office of Science, Science and Technology Facilities Council, Japan Society for the Promotion of Science, Japan Science and Technology Agency, Division of Astronomical Sciences, Integrated Electronics Engineering Center, Binghamton University, Argonne National Laboratory, Fermilab, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory

OpenAlex ID: W7214213845