Testing Feedback Regulated Star Formation in Gas Rich, Turbulent Disk
  Galaxies
  In this paper we compare the molecular gas depletion times and mid-plane
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 ($z\sim0.1$) turbulent disks. We find a strong
correlation, such that galaxies with lower molecular gas depletion time
(t_{dep}) have higher gas velocity dispersion ($\sigma$). Within the scatter of
our data, our observations are consistent with the prediction that depletion
time is inversely proportionate to velocity dispersion made in theories of
feedback-regulated star formation. We also show a strong, single power-law
correlation between mid-plane pressure (P) and star formation rate surface
density (Sigma_{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/Sigma_{SFR} values that are significantly larger than theoretical
predictions. Our observations could be explained with any of the following: (1)
the correlation of \Sigma_{SFR}-P is significantly sub-linear; (2) the momentum
injected from star formation feedback (so-called 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 velocity
dispersion. 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 the internal
regulation of star formation via feedback.
