The Stability of Galaxy Disks

2013/10/18 by Westfall, Kyle B., Andersen, David R., Bershady, Matthew A. +3
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences

paper · doi:10.48550/arxiv.1310.4980

Abstract

We calculate the stellar surface mass density (Sigma_*) and two-component (gas+stars) disk stability (Q_RW) 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 Q_RW=2.0+/-0.9 at 1.5 scale lengths. We also find that Q_RW is anti-correlated with the star-formation rate surface density (Sigma_SFR), which can be predicted using a closed set of empirical scaling relations. Finally, we find that the star-formation efficiency (Sigma_SFR/Sigma_g) is correlated with Sigma_* and weakly anti-correlated with Q_RW. The former is consistent with an equilibrium prediction of Sigma_SFR/Sigma_g propto Sigma_*^1/2. Despite its order-of-magnitude range, we find no correlation of Sigma_SFR/Sigma_g/Sigma_*^1/2 with any other physical quantity derived by our study.

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