Observed non-constancy of the dimensionless star formation rate on the scales of clumps

The star formation rate per free-fall time, ε_ff, is predicted in theories of turbulence-regulated star formation to be low and relatively constant. We follow up on previous analyses by computing ε_ff in nearby molecular clouds using observed protostars (from the SESNA database) and cloud properties (from the HOTT analysis of Herschel observations and from molecular line observations in the GAS and KEYSTONE surveys). While we are able to reproduce the cloud-scale Kennicutt-Schmidt law and ε_ff estimates from previous analyses, we find that an excess scatter in ε_ff correlates with properties of the local cloud environment. Examining 155 individual clumps identified within the cloud data, we find that ε_ff correlates strongly with the clump mass, average density, and virial parameter (Spearman test statistic p<0.001). ε_ff shows some correlation with the presence of OBA stars, but not strongly enough to explain the other relations. We are investigating possible biases introduced by incompleteness and crowding.