paper

Swirls of FIRE: Spatially Resolved Gas Velocity Dispersions and Star Formation Rates in FIRE-2 Disk Environments

arXiv:1911.00020 · doi:10.1093/mnras/staa1619

Abstract

We study the spatially resolved (sub-kpc) gas velocity dispersion ()--star formation rate (SFR) relation in the FIRE-2 (Feedback in Realistic Environments) cosmological simulations. We specifically focus on Milky Way mass disk galaxies at late times. In agreement with observations, we find a relatively flat relationship, with km/s in neutral gas across 3 dex in SFRs. We show that higher dense gas fractions (ratios of dense gas to neutral gas) and SFRs are correlated at constant . Similarly, lower gas fractions (ratios of gas to stellar mass) are correlated with higher at constant SFR. The limits of the - relation correspond to the onset of strong outflows. We see evidence of "on-off" cycles of star formation in the simulations, corresponding to feedback injection timescales of 10-100 Myr, where SFRs oscillate about equilibrium SFR predictions. Finally, SFRs and velocity dispersions in the simulations agree well with feedback-regulated and marginally stable gas disk (Toomre's ) model predictions, and the data effectively rule out models assuming that gas turns into stars at (low) constant efficiency (i.e., per free-fall time). And although the simulation data do not entirely exclude gas accretion/gravitationally powered turbulence as a driver of , it appears to be strongly subdominant to stellar feedback in the simulated galaxy disks.

18 pages, 12 figures, submitted to MNRAS

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