Virial Ratio: Direct Evaluation from Molecular Cloud Data and the Challenges of Improving Accuracy

Abstract

The virial ratio between kinetic and gravitational terms provides key insight into the balance of forces that confine a molecular cloud, but the clumpy and filamentary structures of resolved clouds make it difficult to evaluate this ratio in a consistent way. For clouds with resolved maps of column density as well as a line tracer, we demonstrate that the gravitational energy can be estimated directly from observations in a manner similar to the kinetic energy. This offers improved diagnostic power and consistency. Disentangling a cloud from foreground and background materials is a persistent challenge, for which we introduce a strategy based on Abel's transform. We provide proofs of principle using simulated clouds.