paper

Ergodicity of FIRE: star formation variations within and between simulated galaxies

arXiv:2607.18005 · doi:10.3847/1538-4357/ae80a1

Abstract

We investigate the ergodicity of star formation in simulated galaxies from the FIRE-2 (Feedback In Realistic Environments) project. We restrict ergodicity considerations to being related to deviations from the star-forming main sequence (SFMS), and in turn whether ensemble averages across populations match time-averaged star formation histories (SFHs) based on simulated observable properties. We find that in these high-resolution simulations the deviations of individual galaxies from the SFMS tend to approach ergodic behavior over time, regardless of the SFMS definition adopted and the star formation estimator used. This trend persists when galaxy morphology, as traced by Sérsic index, is considered despite the spheroid-dominated morphologies showing a smaller range of SFMS deviations than the disk-dominated morphologies. Unsurprisingly, we find more rapid convergence to ergodic behavior for star formation estimators based on shorter time scales ( years) as opposed to longer ( years). We caution that these findings should be considered in the context of the current sample and that further studies, particularly of high redshift evolution and the impact of active galactic nuclei should be investigated.

17 pages, 11 figures, 2 tables. Published in ApJ

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