The DiskMass Survey. VIII. On the Relationship between Disk Stability and Star Formation

Type Journal Article
Names Kyle B. Westfall, David R. Andersen, Matthew A. Bershady, Thomas P. K. Martinsson, Robert A. Swaters, Marc A. W. Verheijen
Publication The Astrophysical Journal
Volume 785
Issue 1
Pages 43
Journal Abbreviation The Astrophysical Journal
Date April 1, 2014
DOI 10.1088/0004-637X/785/1/43
ISSN 0004-637X
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Abstract We study the relationship between the stability level of late-type galaxy disks and their star-formation activity using integral-field gaseous and stellar kinematic data. Specifically, we compare the two-component (gas+stars) stability parameter from Romeo & Wiegert (Q RW), incorporating stellar kinematic data for the first time, and the star-formation rate estimated from 21 cm continuum emission. We determine the stability level of each disk probabilistically using a Bayesian analysis of our data and a simple dynamical model. Our method incorporates the shape of the stellar velocity ellipsoid (SVE) and yields robust SVE measurements for over 90% of our sample. Averaging over this subsample, we find a meridional shape of \sigma _z/\sigma _R = 0.51^{+0.36}_{-0.25} for the SVE and, at 1.5 disk scale lengths, a stability parameter of Q RW = 2.0 ± 0.9. We also find that the disk-averaged star-formation-rate surface density (\dot{\Sigma }_{e,\ast }) is correlated with the disk-averaged gas and stellar mass surface densities (Σ e, g and Σ e, *) and anti-correlated with Q RW. We show that an anti-correlation between \dot{\Sigma }_{e,\ast } and Q RW can be predicted using empirical scaling relations, such that this outcome is consistent with well-established statistical properties of star-forming galaxies. Interestingly, \dot{\Sigma }_{e,\ast } is not correlated with the gas-only or star-only Toomre parameters, demonstrating the merit of calculating a multi-component stability parameter when comparing to star-formation activity. Finally, our results are consistent with the Ostriker et al. model of self-regulated star-formation, which predicts \dot{\Sigma }_{e,\ast }/\Sigma _{e,g}\propto \Sigma _{e,\ast }^{1/2}. Based on this and other theoretical expectations, we discuss the possibility of a physical link between disk stability level and star-formation rate in light of our empirical results.
Tags GALAXIES: EVOLUTION, galaxies: kinematics and dynamics, galaxies: spiral, galaxies: star formation
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