2019ApJ...870...46F

In this paper we compare the molecular gas depletion times and midplane hydrostatic pressure in turbulent, star-forming disk galaxies to internal properties of these galaxies. For this analysis we use 17 galaxies from the DYNAMO sample of nearby (z ∼ 0.1) turbulent disks. We find a strong correlation, such that galaxies with lower molecular gas depletion time (t_dep) have higher gas velocity dispersion (σ). Within the scatter of our data, our observations are consistent with the prediction that t_dep∝σ ^–1 made in theories of feedback-regulated star formation. We also show a strong, single power-law correlation between midplane pressure (P) and star formation rate surface density (Σ_SFR), which extends for 6 orders of magnitude in pressure. Disk galaxies with lower pressure are found to be roughly in agreement with theoretical predictions. However, in galaxies with high pressure we find P/Σ_SFR values that are significantly larger than theoretical predictions. Our observations could be explained with any of the following: (1) the correlation of Σ_SFR-P is significantly sublinear; (2) the momentum injected from star formation feedback (p_*/m_*) is not a single, universal value; or (3) alternate sources of pressure support are important in gas-rich disk galaxies. Finally, using published survey results, we find that our results are consistent with the cosmic evolution of t_dep(z) and σ(z). Our interpretation of these results is that the cosmic evolution of t_dep may be regulated not just by the supply of gas but also by the internal regulation of star formation via feedback.