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Spiral Arms are Metal Freeways: Azimuthal Gas-Phase Metallicity Variations in FIRE-2 Galaxies

Presentation #113.01 in the session Spiral Galaxies.

Published onJun 29, 2022
Spiral Arms are Metal Freeways: Azimuthal Gas-Phase Metallicity Variations in FIRE-2 Galaxies

I will present an investigation of the azimuthal variation in gas-phase metallicity in six simulated Milky Way mass spiral galaxies from the FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulation suite near z = 0. Looking at scales ranging from 100 – 750 pc, analogous to modern integral field unit (IFU) galaxy surveys, I map the gas-phase metallicities in both the cold & dense gas, and ionized gas correlated with HII regions. When considering the spatial distribution of metallicity relative to the average at a given radius, I report that the spiral arms alternate in a pattern of metal rich and metal poor relative to the median metallicity on the order of ~0.1 dex, uniformly across this sample of flocculent spirals. This pattern does not correspond with the rate of local star formation, nor does it have a significant correlation with spiral arm passage. Rather, the arms are streaming inwards and outwards relative to each other, carrying the local metallicity gradient with them before mixing. The arms act as freeways channeling relatively metal poor gas radially inwards, and relatively enriched gas radially outwards in a striking, alternating pattern.

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