Gravitational Star Formation Thresholds and Gas Density in Three Galaxies

M.S. Oey and R.C. Kennicutt

It has long been held that the star formation rate (SFR) may be described as a power law of the gas density, as given by Schmidt (1959). The three spiral galaxies in this study have published maps of both H2 (as traced by CO), and H I, thereby enabling us to investigate the relationship between total gas surface density and SFR. The results of these full-disk studies show a remarkable correlation between the total gas density and the threshold densities given by the gravitational stability criterion. In particular, the threshold density appears to mark a lower boundary to the range of gas densities in these galaxies.