The Stability of Galaxy Disks
Abstract
We calculate the stellar surface mass density (Sigma*) and two-component (gas+stars) disk stability (QRW) for 25 late-type galaxies from the DiskMass Survey. These calculations are based on fits of a dynamical model to our ionized-gas and stellar kinematic data performed using a Markov Chain Monte Carlo sampling of the Bayesian posterior. Marginalizing over all galaxies, we find a median value of QRW=2.0+/-0.9 at 1.5 scale lengths. We also find that QRW is anti-correlated with the star-formation rate surface density (SigmaSFR), which can be predicted using a closed set of empirical scaling relations. Finally, we find that the star-formation efficiency (SigmaSFR/Sigmag) is correlated with Sigma* and weakly anti-correlated with QRW. The former is consistent with an equilibrium prediction of SigmaSFR/Sigmag propto Sigma*1/2. Despite its order-of-magnitude range, we find no correlation of SigmaSFR/Sigmag/Sigma*1/2 with any other physical quantity derived by our study.
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