Abstract
We estimate the parameters of the Kennicutt-Schmidt (KS) relationship, linking the star formation rate (ΣSFR) to the molecular gas surface density (Σmol), in the Survey Toward Infrared-Bright Nearby Galaxies sample of nearby disc galaxies using a hierarchical Bayesian method. This method rigorously treats measurement uncertainties, and provides accurate parameter estimates for both individual galaxies and the entire population. Assuming standard conversion factors to estimate ΣSFR and Σmol from the observations, we find that the KS parameters vary between galaxies, indicating that no universal relationship holds for all galaxies. The KS slope of the whole population is 0.76, with the 2σ range extending from 0.58 to 0.94. These results imply that the molecular gas depletion time is not constant, but varies from galaxy-to-galaxy, and increases with the molecular gas surface density. Therefore, other galactic properties besides just Σmol affect ΣSFR, such as the gas fraction or stellar mass. 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.
Author
Shetty, Rahul; Kelly, Brandon C.; Rahman, Nurur; Bigiel, Frank; Bolatto, Alberto D.; Clark, Paul C.; Klessen, Ralf S.; Konstandin, Lukas K.
Journal
Monthly Notices of the Royal Astronomical Society: Letters
Paper Publication Date
January 2014
Paper Type
Astrostatistics