1306.2951 (Rahul Shetty et al.)

Indications of a sub-linear and non-universal Kennicutt-Schmidt relationship    [PDF]

Rahul Shetty, Brandon C. Kelly, Nurur Rahman, Frank Bigiel, Alberto D. Bolatto, Paul C. Clark, Ralf S. Klessen, Lukas K. Konstandin

We estimate the parameters of the Kennicutt-Schmidt (KS) relationship in the STING sample of nearby disk galaxies using the hierarchical Bayesian method developed by Shetty et al. This method rigorously treats measurement uncertainties, and provides accurate parameter estimates for individual galaxies as well as the entire population. We find that the KS parameters vary between galaxies, indicating that no universal relationship holds for all galaxies. Additionally, in eight galaxies the KS relationship is sub-linear at 95% confidence. The KS slope of the whole population is 0.76, with the 95% extent [0.60, 0.92]. This suggests that the molecular gas depletion time is not constant, but varies from galaxy to galaxy, and increases with the molecular gas surface density. These results suggest that other galactic properties besides just the gas surface density, such as gas fraction or stellar mass, affect the star formation rates. The non-universality of the KS relationship indicates that a comprehensive theory of star formation must take into account additional physical processes that may vary from galaxy to galaxy.

View original: http://arxiv.org/abs/1306.2951