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Abstract
Baryonic cycling is reflected in the spatial distribution of metallicity within galaxies; however, gas-phase metallicity distribution and its connection with other properties of dwarf galaxies are largely unexplored. We present the first systematic study of radial gradients of gas-phase metallicities for a sample of 55 normal nearby star-forming dwarf galaxies (stellar mass M_⋆ ranging from 10^7 to 10^9.5 M_⊙) based on MUSE wide-field spectroscopic observations. We find that the metallicity gradient has a significant negative correlation (Spearman's rank correlation coefficient r ≃ -0.56) with M_⋆, which is in contrast with the flat or even positive correlation observed for higher-mass galaxies. The negative correlation is accompanied by a stronger central suppression of metallicity compared to the outskirts in lower-mass galaxies. Among the other explored galaxy properties, including baryonic mass, star formation distribution, galaxy environment, regularity of gaseous velocity field, and effective yield of metals rm y_ eff only the regularity of gaseous velocity field and rm y_ eff have residual correlation with metallicity gradient after controlling for M_⋆, in the sense that galaxies with an irregular velocity field or lower rm y_ eff favor a less negative or more positive metallicity gradient. Particularly, a linear combination of logarithmic stellar mass and rm y_ eff significantly improves the correlation with metallicity gradients (r ∼ -0.68) compared to using stellar mass alone. The lack of correlation with environment disproves gas accretion as a relevant factor shaping the metallicity distribution. The correlation with both gaseous velocity field regularity and rm y_ eff implies the importance of stellar feedback-driven metal redistribution within the ISM. Our finding suggests that the metal mixing and transport process, including but not limited to feedback-driven outflow, are more important than in situ metal production in shaping the metallicity distribution of dwarf galaxies.
Published Version
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