Schmidt's Conjecture and Star Formation in Galactic Molecular Clouds and Galaxies
Charles Lada

Ever since the pioneering work of Martin Schmidt a half-century ago there has been great interest in finding an appropriate empirical relation that would directly link some property of interstellar gas with the physical process of star formation within it. Schmidt conjectured that this might take the form of a relation between the rate of star formation (SFR) and the surface density of the interstellar gas. In this talk I will describe how recent observations of nearby GMCs are now providing new insights into the nature of this relationship. I will show that, although a Schmidt relation is observed within individual molecular clouds, there is no Schmidt law that characterizes star formation between clouds. Instead, a linear scaling relation exists connecting the total SFR and the amount of dense gas within GMCs. This scaling law may be the underlying physical relationship that most directly links star formation activity with molecular gas both between GMCs in the Milky Way and within and between external galaxies. Finally I will discuss the implications of these results for understanding the nature of the Kennicutt-Schmidt law for galaxies.