Galaxies Below the Fundamental Metallicity Relation Are Morphologically Disturbed: Merian Hα Morphologies and DESI Metallicities

@misc{mintz2026galaxies,
  title = {{Galaxies Below the Fundamental Metallicity Relation Are Morphologically Disturbed: Merian H$α$ Morphologies and DESI Metallicities}},
  author = {Abby Mintz and Jenny E. Greene and Shany Danieli and Erin Kado-Fong and Alexie Leauthaud and Jiaxuan Li and Yifei Luo and Annika H. G. Peter and Joy Bhattacharyya and Mingyu Li and Akaxia Cruz},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.26887},
  eprint = {2609.26887},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.26887},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Galaxies Below the Fundamental Metallicity Relation Are Morphologically Disturbed: Merian Hα Morphologies and DESI Metallicities
AU  - Abby Mintz
AU  - Jenny E. Greene
AU  - Shany Danieli
AU  - Erin Kado-Fong
AU  - Alexie Leauthaud
AU  - Jiaxuan Li
AU  - Yifei Luo
AU  - Annika H. G. Peter
AU  - Joy Bhattacharyya
AU  - Mingyu Li
AU  - Akaxia Cruz
PY  - 2026
DA  - 2026/09/22
PB  - arXiv
DO  - 10.48550/arxiv.2609.26887
UR  - https://arxiv.org/abs/2609.26887
AB  - 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 Hα emission for a large sample of galaxies with DESI DR1 spectra, reaching stellar masses down to 10^8 M_⊙. 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 Hα 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.
ER  -